Many of the books have excellent photos.
The Aqualogs are great for helping to ID species
Although many have out dated scientific names, I don't see this as problematic, because the species name hardly ever changes,( just the genus), as DNA sequencing advances. So if one follows the current lit, not a problem.
Some hardly have any photos at all, like "The Cichlid Fishes, Natures Grand Experiment in Evolution" by George Barlow, which I find to be one of "the" most informative.
These books are written by experts in their field, and I find them invaluable, compared to internet info, that at times is an opinion provided by someone who has kept a fish for a year or less and thinks they are thus qualified to respond. But a few months or a year or two, is not real experience IMO
Most cichlids and other large fish species have a life span of 10 years, and take 3 or more years to mature, so unless the keeper has kept a certain species at least 3-5 years, I consider their experience with that species is often highly questionable.