There is no definitive list of “best” books to learn from, and I don’t want to try to provide one. There are many books out there, and none are really comprehensive. This means you should look for multiple books where you can understand the way the content is presented and explained.
I’m going to offer a few examples but would urge you to consider all resources as you choose books to study from. You should also seek out theory books designed for the instrument you play, and you should plan on using more than one book. Music Teachers can be a useful source of book recommendations.
For example, if you are a drummer you will want to study rudiments as part of your theory training. The following books seem like they might be useful: Stick Control for the Snare Drummer by George Lawrence Stone; Groove Alchemy by Stanton Moore; The Drum Rudiment Bible: 500 Rudiments Beginner to Advanced by D. Agostinelli, Modern Reading Text In 4/4 by Louis Bellson, and The Drummer’s Complete Vocabulary As Taught by Alan Dawson.
For guitar, I benefitted greatly from Leon White’s series of books on music theory, chord structures, studio music styles, and improvisation. I’d also recommend the Berklee Press books for guitar theory. I like Mark Baxter’s voice lesson books and he also has excellent free training videos on his website.
You will find music theory books geared to every instrument. There’s no shortage of authoritative sources for books, video courses, and DVDs to learn theory for any level and instrument (including voice).
You will also find numerous blogs and articles online with clear explanations of various music theory topics. Just Google. (Or check out our existing articles on “Why Do We Learn Music Theory?” and “Music Theory for Beginners: The Simple Way.”)
You can find many books used online for just a few dollars. I recommend you pick up an abridged music dictionary, such as the Harvard Dictionary of Music as it is useful to have on hand to look up any terms you come across you aren’t sure of the meaning for. Mark McGrain’s Music Notation is an outstanding workbook to learn how to draw all the music symbols.
It makes a great reference book as well if you ever need to look up how to notate something. There are software notation programs such as Finale and Sibelius you might also find useful to learn more about music notation.
If you know any Music Teachers or professional musicians, ask them for their top recommendations. Study prominent music schools’ websites for suggested learning materials. Lastly, don’t discount the usefulness of magazine articles and blogs. If you search, you will find many shorter, well-written articles with clear examples in them for free. Use them.