One of the best books is the Boatowners Mechanical and Electrical Manual by Nigel Calder. https://www.amazon.com/dp/0071790330/ref=cm_sw_r_cp_api_glc_fabc_zno8FbSH6DCYF Most systems on an older boat are repairable by someone willing to dive in and learn. Baba’s and HR’s are both excellent choices. Have fun thermoscap!
If you are new to sailing, try The Book on Sailing Safety. It teaches the fundamentals of sailing and boating safety as well as more advanced topics. Search for it on Amazon
Not sailing specific, but "On Rope" by Bruce Smith and Allen Padgett was my first real exposure to Knot Tying. I was a member of the National Speleological Society at the time, and also knew Allen from Hang Gliding at Lookout Mountain Flight Park.
Then, my wife bought me The Ultimate Encyclopedia of Knots and Ropework. I love this book. It's not too huge, and covers quite a range of knots and rope techniques.
I also have a PDF version of Ashleys.
Great book if you want to sail fast! Not only does it give tips on technique, it also helps you with weather pattern recognition and design advantages/disadvantages. I highly recommend it!
Also check out the sequel: Higher Performance Sailing