sometimes i read up to 4 books, at least 2 are fiction (because library in high school allowed that maximum), sometimes none (like nowadays). Haven't found much time to read since I started music 3 years ago, but I have a music history course now so I HAVE to read sooner or later.

History is NOT my favorite subject.
I don't use bookmarks, most are so thick they crease the spine over time. I hate that, and for new books I am extra careful with turning pages. I don't know if you have them, but I use thin, flexible used phone cards, so it saves money too.
I find it most efficient to switch books every few minutes, before you get tired of one, and find that you read more at the end of the day than if reading just one at a time. But HOW I read really depends on the book:
1. for studying - study one topic. underline and highlight as i go, write comments on the margins or notebook
2. fiction - just read from start to finish, visualizing the story as i go (dreaming of it at night too)
3. music books - just throw them out the window