Before my recent dive trip to Fiji I looked for a good fish ID book for the area (one with photos, not paintings) and came up short. It doesn't seem like anyone has done a comprehensive reference for this area comparable to Humann's works on the Caribbean.
However, I did find Paddy Ryan's fine volume in the lending library at the resort where I was staying. To my surprise, I find it to be much more than the typical, superficial "snorkeler's guide." It's a small but beautifully produced volume with excellent photography and a well-written text. It's a good balance of photos to help identify the most common South Pacific reef fish combined with informative text on the behavior and biology of reef fish, other vertebrates, and invertebrates.
I didn't buy a copy when I had a chance in a local shop, and I regretted it on the long flight home. I'm buying my personal copy as soon as I finish writing this. Take my word for it, for snorkelers, novice divers! , or serious divers, this is money well spent!