(Note: I may update this post occasionally as I encounter further books.)
A little over two months ago, I decided to learn to draw, at least enough to depict a recognizable face. Being of a scholarly temperament, that quickly expanded into reading everything I could easily find about how to draw humans, rather than actually practicing drawing, which consensus says is the best way to learn to draw. Well, I still intend to practice, just as soon as I'm finished with this book... and that one...
Unfortunately, there are quite a few poor art tutorial books available, and the good ones are not so easy to find. As far as approach, most divide into one of two camps.
The first is the depiction camp, focusing on being able to draw what you see. The hardest part of this is seeing. This camp is ably led by Betty Edwards of Drawing on the Right Side of the Brain, who tells you up front that she is not going to tell you how to draw from memory or imagination. This is a good place to start if you don't think you can draw, because the truth is that you probably can and that it's actually not difficult to learn -- not to imply that it's easy to do -- you simply have to take time and care in accurately seeing the values and proportions of what's in front of you, and copying them onto paper. This leads to fast results, but is limited compared to what you can do by construction. Maughan and Hammond are also in this camp, based on the very limited representation of their books I've seen (Maughan's Artist's Complete Guide to Drawing the Head, which isn't complete at all, and Hammond's book on drawing portraits with colored pencil, which I didn't even bother to check out of the library, though I might in the future for the discussion of color).
The second is the construction camp. Pretty much every book aimed at serious (not to imply professional) artists goes this route: understanding the structure of what you want to depict rather than merely copying it. Robert Beverly Hale, George Bridgman, Burne Hogarth are all in this camp, though some are more able teachers than others. Construction is by far the more powerful approach, but requires a correspondingly larger investment in the artist's education. I started with the wrong book in this class and was horribly confused by the discussions of masses and planes that are nearly universal. Hale's Drawing Lessons from the Great Masters seems to be a pretty good place to start, though he is opinionated.
There are also anatomy reference books, which are predicated on the assumption that you want to be able to construct a human figure; I don't consider myself to be at a point where I can judge most of these adequately, though Gary Faigin's book on facial expressions is absolutely fascinating and Valerie Winslow's Classic Human Anatomy seems nearly comprehensive for general body structure, though it lacks much information about sex and age differences. Terence Coyle's Anatomy Lessons from the Great Masters (it has Hale's name on the front, but it's by Coyle) has a more concise, but less comprehensive discussion illustrated by classic drawings.
Finally, there are technique books. Several of the above mention or even recommend some techniques, both as far as media (graphite? charcoal? using a prepared ground?) and drawing (gesture drawing, contour drawing, crosshatching); many other books only seem to discuss the technique without discussing the ideas behind it. Michael Wood's Starting Pencil Drawing and Stan Smith's Drawing: The Complete Course were two that I found in the library. Both have some good ideas, sometimes between the lines, but cover the techniques of drawing more than how to see or know what you are drawing. Contour drawing, for example, is a worthwhile exercise because it forces you to look at the object you're depicting rather than the result on paper, but not every book that suggests it as an exercise explains this! Wood's book is notable for suggesting varying the width of lines to suggest shadows, and for advising the reader to use tone rather than lines to depict volumes more realistically (lines, after all, only exist as ideas, not in the real world), but probably isn't worth keeping. Smith's book covers various techniques like prepared grounds, ink drawings, washes, erasing, systems of proportions and ways to measure them when drawing from life, repairing damaged drawings, etc., but seems more about hands-on direction and practice copying than the theory that would let you tackle projects of your own (instead of his prepared projects). It does include a page depicting the proportions of children at 3 or 4 different ages, which might be of some interest.
In practically all of these cases, the student is left to determine which exercises to do and what to practice on their own. Betty Edwards book has actual exercises; Hale is rather opinionated about what students should practice; but most other books suggest exercises less directly, with some only telling how they do things and leaving you to figure out how to practice that yourself. Stan Smith's book has a project with four basic shapes (sphere, cube, cylinder, cone) but doesn't, if I recall correctly, explain that practicing those at various angles is valuable for more than just the ability to shade them correctly; it's an important step in being able to draw constructed figures.
Bottom line: of reading many books there is no end, but it's probably a better use of your time to get one or two (Edwards and Hale are the two I'd recommend) and use the time you would have spent reading the others to practice. I expect the anatomy references are more useful once you have basic skills, but I'm not there yet!
And an aside: While I was at the art store to get a 4B pencil and a kneaded eraser, I picked up a cheap Manuscript fountain pen aimed at calligraphy. The same lessons about seeing that apply to drawing apply here: if you focus on copying an alphabet like the chancery Italic J. Pickering uses, and don't rush, it really isn't that hard. Edwards book actually has an afterword or appendix that discusses handwriting. As a bonus, letters are easier to draw recognizably than faces, so satisfactory results require less work. Margaret Shepherd's book Learn Calligraphy seems to have a pretty good selection of alphabets, and there are also many resources online, such as IAMPETH (esp. good for Spencerian, I've heard, though I haven't tried it yet) and the Fountain Pen Network forums.