For DIY projects and mechatronics modding you can surely refer to the latest, just released “Robot Builder’s Bonanza” 5th ed. book, here from Amazon https://www.amazon.com/Robot-Builders-Bonanza-Gordon-Mccomb/... . More in general, it depends on what you do want to achieve: reinforcement learning is the latest hottie with small robotics and a very good academic lab with a lot of public materials is in Zurich at ETH http://rpg.ifi.uzh.ch

Topping my list: “Robot Builder’s Bonanza” 5th ed. by Gordon McComb and McGraw Hill, out worldwide in mid Dec https://www.amazon.com/Robot-Builders-Bonanza-Gordon-McComb/...