IMO ....
For fishes, Scott Michael's Reef Fishes series, else one of his pocket guides. I've found his advice dependable + tank sizing realistic.
If beginning, I liked Tullocks Natural Reef Aquariums ... otherwise for `general' books the newest Sprung/Delbeek `The Reef Aquarium' Vol 3 sure looks good [I have 1 + 2].
Coral-wise, I still defer to Eric Borneman's Aquarium Corals book ... those little guide books just lack so much important information and gloss over differences among Genus/etc.
JMO ... I'd strongly encourage books, as they'll easily save you their cost through avoiding problem livestock.