It can also be done without reading.
When I studied with Ed (before he wrote his books) the goal wasn't on grooves but just keeping my time steady. He suggested using a drum machine playing rimshots as a metronome because most metronomes don't go
really slow (my Seiko only gets to 40 bpm). That way at a tempo of 80bpm, playing a rimshot only on beat 1 gives a 20bpm click. Playing the rimshot on 1 and 3 gives a 40 bpm click, etc.
Play something you don't need to think about, like a scale or arpeggio in quarter notes and pay attention to lining each note up with the click. At 20 bpm that’s brutal.
Or you can play at 80 bpm or slower but with the rimshot playing only on the 1 instead of all four beats. Then try it only on the 2, only on the 3, only on the 4. You might be surprised how hard it is to follow a metronome at slow tempos when it only clicks on 2 or 4, 3 isn’t too difficult.
Once you can play for 5 minutes straight with zero mistakes (be honest!), try ticking the tempo up. Try playing at 160 bpm or higher with the rimshot only on 2 if you want a real challenge
Then try stuff like treating the click a 1 of the first bar but
not the next. That way you have to play eight quarter notes before the next click. You can then create all kinds of similar exercises on your own, like setting the time signature to 3/4, 5/4, etc., or the click only coming every four bars, every eight bars, etc., and using eighth or sixteenth notes rather than quarter notes.