The easier it is to absorb information in a book the better. For me a book is valuable because of what it contains, if it remains closed it isn’t helping me learn. For this reason I have my instructional books spiral bound. I get STAPLES or KINKOS to cut the spine off and spiral bind it for around $2.50. 
This makes the book MUCH easier to manage. I can put it on my easel and I don’t have to fight to have the book stay open to see the illustrations I want to learn from.
I also do this with smaller sized books like George Bridgeman’s book on Life Drawing and John Vanderpoel’s The Human Figure, two of my all time favorites. I like to have these two books with me when go to drawing workshops. Often in these type of situations I like to sketch from the books when the model is at break or if I get to the workshop early. Spiral binding the books allows me to easily hold it in my hand while drawing with the other.
The Bridgman book is more for construction/Anatomy and the drawings in it are mainly linear. The Vanderpoel book is more about the refinement of anatomy, most of the drawings are tonal and the Charles Bargue book is all about simplifying complex forms. It is both linear and tonal. All three of these books I HIGHLY recommend. I however cannot end this post without recommending probably the best instructional author of them all: Andrew Loomis. Head and Hands and Figure Drawing for all its Worth probably his best works cover just about everything but the strength of his books lies in his finishes. He has the best looking finished drawings. These books have been out of print for a while but recently they have been reprinted and you can now order them from Amazon or wherever.I have included associate links for each of the books below. Enjoy!
