https://github.com/mmp/pbrt-v3
That said, IMHO, there is no "clean" C++ code. There are C++ codebases that use different styles, and their "quality" more or less is context sensitive.
Personally I felt the best tutorial to C++ were actually two other programming languages - Scheme and F#.
Scheme drove in the concept that it's totally fine to model things based on the shape of the data and that you don't need to create type based abstractions around every thing.
F# then demonstrated how a language with type system is supposed to work.
The problem with C++ is that the language is so verbose that unless you have an abbreviated model in your head how a type based language can be used to solve problems in best way, you will get lost in trivial C++ minutiae.
So, personally, I generally think "Am I solving a Scheme like problem or Standard ML like problem" and then try to apply C++ as simply as possible.
Several academics have created a career of how to patch C++/Java/C# with concepts that make them less fragile in a collaborative context:
https://en.wikipedia.org/wiki/Design_Patterns
https://www.amazon.com/Design-Patterns-Elements-Reusable-Obj...
In my opinion design patterns are not a fundamental concept, but rather provide common syntax for collaboration purposes for various patterns that are parts of language and more or less invisible in e.g. Scheme or F#. But if one is diving into C++ it's probably convenient to be familiar with these concepts.
https://www.amazon.com/Design-Patterns-Elements-Reusable-Obj...
https://www.amazon.com/Refactoring-Improving-Design-Existing...
EDIT: And it appears the website is a direct rip-off of these books.
Practical Object-Oriented Design in Ruby by Sandi Metz. http://www.poodr.com/
And Kent Beck's http://www.amazon.com/Smalltalk-Best-Practice-Patterns-Kent/...
Design patterns are the greatest tool there is for learning software design. If you know them, you can apply them, but much more importantly they show you how you can apply the basic principles of OO development to various problems. By learning them, you're learning the thought process of how they came to be, and you'll be able to apply those thought processes to your own problems. Consider it like learning algebra by doing exercises. You can read theory all you like, but unless you apply it it just won't click.
"Favor object composition over class inheritance"
[1] http://www.amazon.com/Design-Patterns-Elements-Reusable-Obje...
Effective Java — http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp...
POODR (Ruby) — http://www.poodr.com/
Javascript the good parts — http://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockfor...
There is of course also the gang of 4 language agnostic classic on design patterns http://www.amazon.com/Design-Patterns-Elements-Reusable-Obje...
- Effective C++: http://www.amazon.com/Effective-Specific-Improve-Programs-De...
In no particular order:
1- http://www.amazon.com/C-Programming-Language-2nd-Edition/dp/...
2- http://www.amazon.com/The-Answer-Book-Solutions-Programming/...
3- http://www.amazon.com/The-Standard-Library-P-J-Plauger/dp/01...
4- http://www.amazon.com/C-Traps-Pitfalls-Andrew-Koenig/dp/0201...
5- http://www.amazon.com/Expert-Programming-Peter-van-Linden/dp...
6- http://www.amazon.com/Data-Structures-In-Noel-Kalicharan/dp/...
7- http://www.amazon.com/Data-Structures-Using-Aaron-Tenenbaum/...
8- http://www.amazon.com/Mastering-Algorithms-C-Kyle-Loudon/dp/...
9- http://www.amazon.com/Code-Complete-Practical-Handbook-Const...
10- http://www.amazon.com/Design-Patterns-Elements-Reusable-Obje...
11- http://www.amazon.com/The-Mythical-Man-Month-Engineering-Ann...
12- http://www.amazon.com/The-Programming-Language-4th-Edition/d...
13- http://www.amazon.com/The-Standard-Library-Tutorial-Referenc...
14- http://www.amazon.com/API-Design-C-Martin-Reddy/dp/012385003...
15- http://www.amazon.com/The-Linux-Programming-Interface-Handbo...
16- http://www.amazon.com/Computer-Systems-Programmers-Perspecti...
17- http://www.amazon.com/System-Programming-Unix-Adam-Hoover/dp...
18- http://www.amazon.com/Memory-Programming-Concept-Frantisek-F...
19- http://www.amazon.com/Memory-Management-Implementations-Prog...
20- http://www.amazon.com/UNIX-Filesystems-Evolution-Design-Impl...
21- http://www.amazon.com/PCI-System-Architecture-4th-Edition/dp...
22- http://www.amazon.com/Universal-Serial-System-Architecture-E...
23- http://www.amazon.com/Introduction-PCI-Express-Hardware-Deve...
24- http://www.amazon.com/Serial-Storage-Architecture-Applicatio...
25- http://www.amazon.com/SATA-Storage-Technology-Serial-ATA/dp/...
26- http://www.amazon.com/Beyond-BIOS-Developing-Extensible-Inte...
27- http://www.amazon.com/Professional-Assembly-Language-Program...
28- http://www.amazon.com/Linux-Kernel-Development-3rd-Edition/d...
29- http://www.amazon.com/Version-Control-Git-collaborative-deve...
30- http://www.amazon.com/Embedded-Software-Primer-David-Simon/d...
31- http://www.amazon.com/Programming-Embedded-Systems-C/dp/1565...
32- http://www.amazon.com/Making-Embedded-Systems-Patterns-Softw...
33- http://www.amazon.com/Operating-System-Concepts-Abraham-Silb...
34- http://www.amazon.com/Performance-Preemptive-Multitasking-Mi...
35- http://www.amazon.com/Design-Operating-System-Prentice-Hall-...
36- http://www.amazon.com/Unix-Network-Programming-Sockets-Netwo...
37- http://www.amazon.com/TCP-Illustrated-Volume-Addison-Wesley-...
38- http://www.amazon.com/TCP-IP-Illustrated-Vol-Implementation/...
39- http://www.amazon.com/TCP-Illustrated-Vol-Transactions-Proto...
40- http://www.amazon.com/User-Interface-Design-Programmers-Spol...
41- http://www.amazon.com/Designing-Interfaces-Jenifer-Tidwell/d...
42- http://www.amazon.com/Designing-Interfaces-Jenifer-Tidwell/d...
43- http://www.amazon.com/Programming-POSIX-Threads-David-Butenh...
44- http://www.intel.com/p/en_US/embedded/hwsw/software/hd-gma#d...
45- http://www.intel.com/content/www/us/en/processors/architectu...
46- http://www.intel.com/p/en_US/embedded/hwsw/hardware/core-b75...
47- http://www.hdmi.org/index.aspx
48- http://en.wikipedia.org/wiki/Digital_Visual_Interface
49- http://www.amazon.com/Essential-Device-Drivers-Sreekrishnan-...
50- http://www.amazon.com/Making-Embedded-Systems-Patterns-Softw...
51- http://www.amazon.com/Python-Programming-Introduction-Comput...
52- http://www.amazon.com/Practical-System-Design-Dominic-Giampa...
53- http://www.amazon.com/File-Systems-Structures-Thomas-Harbron...
54- ...well, I'll stop here.
Of course, the equivalent knowledge can be obtained by trial-and-error, which would take longer and might result in costly errors and imperfect design. The greater danger here is that a sole developer, without the feedback and interaction of even a small group of capable and experienced programmers could simply burn a lot of time repeating the mistakes made by those who have already trenched that territory.
If the goal is to write a small RTOS on a small but nicely-featured microcontroller, then the C books and the uC/OS book might be a good shove in the right direction. Things start getting complicated if you need to write such things as a full USB stack, PCIe subsystem, graphics drivers, etc.
Rinse repeat. You'll find that once you have one language down, the process will go much faster with the second. The features and syntax of most languages are pretty similar.
You can pick any language you like to start with, but personally I'd recommend starting with a hard typed compiled language rather than a dynamic language. Dynamic languages are easy to learn, but its easy to be a lazy and bad programmer in them. They let you get away with too much. Hard typed compiled languages are a) much better at catching your errors and b) much harder to be a lazy programmer in. They don't let you get away with things nearly as much.
I'd recommend Java, seems to be the language a lot of people start with. It will also give you a good founding in open source programming. I started with C/C++ and I'm glad I did. But that was more of a challenge - had to learn pointers and memory management in my first language. And after that I took a little while to learn the open source mindset, since I'd started in a procedural language.
Once you have a good grasp of an object oriented language like Java (or Python) and what object oriented programming means, then I'd recommend reading the Gang of Four book on Design Patterns (http://www.amazon.com/Design-Patterns-Elements-Reusable-Obje...) and Martin Fowler's book on Refactoring (http://www.amazon.com/Refactoring-Improving-Design-Existing-...). Those will give you a pretty good basis in software design and maintenance.
In terms of recommended reading for learning a language, the O'Reilly books are nearly always good in my experience. Here's one for Java (Learning Java: http://www.amazon.com/Learning-Java-Patrick-Niemeyer/dp/0596...) and here's one for Python (Learning Python: http://www.amazon.com/Learning-Python-Powerful-Object-Orient...)
Honestly, the discussion of pros/cons and then the use in industry sections make this book a very good read. It won't be quite as entertaining as lippert's blog, but then again it is a Textbook
[0] https://www.oreilly.com/library/view/design-patterns-element...