I liked GTD, but in my opinion the system laid out in "Total Workday Control Using Microsoft Outlook" is much better: https://www.amazon.com/Total-Workday-Control-Microsoft-Outlo...

I was not a fan of Outlook before I came across this book, but the way the author configures Outlook and the workflows he lays out works really, really well. My inbox is near zero throughout the day, actionable items are captured easily, and tasks don't get lost over time.

I highly recommend it.