Not the original poster, but I learn best reading textbooks cover-to-cover.
A couple things that help me:
1) I buy physical textbooks and absolutely destroy them with notes in the margins, highlighting, etc. It helps me to interact with the material instead of letting it wash over me, which means I'm both thinking about it more in-depth and as side effect I'm less bored. Otherwise I'll fall asleep and won't learn anything.
2) I accept that I'm not going to remember the entire book. A lot of books are most useful as references anyway. But if you ever find yourself going, "Oh that's really handy to know," then you can make a special note of it or even put it into flashcards. I've been using Anki. The trick is to recognize what is actually worth doing this for.
3) If something is especially worth knowing, (see point 2), see if you can either do problems from the book or try out the concept in some way if there are no problems available.
If you're reading something just because you feel like you should, you won't get anything out of it (or a least I don't).
1) I buy physical textbooks and absolutely destroy them with notes in the margins, highlighting, etc. It helps me to interact with the material instead of letting it wash over me, which means I'm both thinking about it more in-depth and as side effect I'm less bored. Otherwise I'll fall asleep and won't learn anything. 2) I accept that I'm not going to remember the entire book. A lot of books are most useful as references anyway. But if you ever find yourself going, "Oh that's really handy to know," then you can make a special note of it or even put it into flashcards. I've been using Anki. The trick is to recognize what is actually worth doing this for. 3) If something is especially worth knowing, (see point 2), see if you can either do problems from the book or try out the concept in some way if there are no problems available.
If you're reading something just because you feel like you should, you won't get anything out of it (or a least I don't).