“Whuh— this is just a bunch of snare drum rhythms... what's the big deal? What am I supposed to do with that?”
Mainly: It's not the book so much as it is the method used with it, which is the best method for learning to improvise and read musically on the drums. You read the rhythms in the book, and, using a galaxy of creative interpretations, create a complete drum set part from it. It's the primary method many good drummers use to play amazing-sounding stuff with minimal mental effort, while still sounding musical.
Also: You're learning to read rhythms the way they are written by professional writers and arrangers, the way they will appear on professional charts.
You learn to play off of a single, changing melodic line— like, a complicated one 32 bars long, figuring out complex interpretations on the fly. Once you've done several of those, improvising becomes very easy.
You learn to think like a horn, conceiving your drumming in terms of a single melodic line. It's a big deal for your musicianship when you think of your drumming that way— even complex, four-limb textures— and not just as a bunch of drum parts.
The format reinforces reinforces thinking in four bar phrases. In Reed, even the one-measure patterns are written out in four measure phrases. You get used to seeing four measures at a time, and you get used to moving your eye along the page even when you're reading something easy.
Even if you don't think you'll ever need to read music when you're playing, this reading-based method is still the best way to learn to play. While you're learning to read, count, and play these rhythms, you're also learning to hear them; and listening is your primary means of fitting in with the music around you, whether you're not using a chart or not. Learning through reading this way gives you clarity about what you're doing, while reducing it to its simplest form mentally, freeing you to concentrate on the music.
“Buh-but, what about all the things that are missing? Complicated 16th note rhythms, meters other than 4/4, triplet partials, quarter note triplets, etc?”
I like to give my hypothetical questioners a stammer. The point is well taken regarding other meters, and quarter note triplets. I'd like to have seen some two-measure rhythms, and some things developing meter-within-meter ideas, too. I've also had need for Reed-type exercises adapted to certain styles, with a limited range of note values, and of varying rhythmic density. I've made up some reading rules, and written up a lot of pages of exercises, and picked up some other books to cover some of those things.
The absence of 16th note rhythms is not so glaring as it seems— you can arrive at similar rhythms by playing the book in 2/2. Reed rhythms in 2/2 are functionally like complex 16th note rhythms in 4/4. True, you're not getting used to seeing the actual 16th note rhythms on the page; for that you could buy Louis Bellson's book, or use the exercises in The New Breed. I personally don't get very many charts written with those types of rhythms.
About the triplet partials— mainly the middle note of the triplet, or the last two notes of the triplet: the book is really about interpreting melodies, and we don't really see those written into melodies often. I've told you how I feel about the middle of the triplet. I don't feel it's a terrible omission. And we do play those notes with many of the interpretations, we just aren't reading them.
“OK, I get that, JEEZ! But there's hardly any words in it! I have a ton of questions!”
There are a lot of other ways to get your specific questions answered— talking to people, listening to music, and playing music. And, as a last resort, other books. It is quite possible to be an excellent drummer with very little defined verbal information. What we get in Syncopation is not verbal information, but an extremely versatile and efficient universal method for playing the drums, and interacting with music creatively.