For sure, blennies are among the most loved and photographed underwater subjects, perhaps second only to nudibranchs!
I recommend this book by marine biologist Francesco Tiralongo, published in 2020 and published in English and Italian. 
The book is specific to the Mediterranean but many species are far more widespread.
A book that cannot be missed in the library of a diver with a passion for macro photography.

 

 

 

Quote

In the Mediterranean Sea, blennies represent an important group of fishes, both in terms of number of species and ecological role. Especially since the last decade, with the spread of the underwater photography, these fishes are relatively well known by amateur and professional photographers and often they represent one of the main subjects in photography. Instead, from the point of view of marine science, their particular reproductive biology and ecology are among those that arouse the most interest. However, in all cases, these little fishes are not always easy to identify and are a challenge both for amateurs and specialists alike. Blennies are beautiful fishes, treasures of the seas, sea creatures that have fascinated me since childhood. The wonderful colors of many of these species often leave the diver surprised and amazed in front of these amazing creatures whose sexual dimorphism of some species fascinates more and more.Blennies of the Mediterranean Sea is an outstanding reference book, accessible and engaging. Francesco Tiralongo teaches us masterfully how to distinguish each species but also what it means to be a blenny, considering biological and ecological details. About sixty color illustrations and sixty hand-made drawings and details of the key taxonomic characters will guide the reader towards a rapid, easy and certain identification of 31 species (plus some Atlantic species), which can be found in Mediterranean waters. This Guide is a fundamental reference for Mediterranean ichthyologists and a useful and inspiring tool for anyone else interested in the field of marine biodiversity, such as divers, fishermen and other sea lovers. Nomina si nescis, perit et cognitio rerum (Linneus, 1755). If you do not know the names of things, the knowledge of things themselves perishes. This was the fundamental principle of taxonomy, the science of describing, naming, and classifying living organisms. This was also the merit of this book, a wonderful contribution to the knowledge and conservation of this fascinating and understudied group of marine species.

 

 

With the author's permission, I post some photos of the book here.

 

 

 

 

 

 

Worth adding to the book list, Davide?

Do you mean Kraken's list?

That is a photographic tecnique list.

Maybe it worths a list on the id section.

Know your species...

Yeah, good point. I was thinking it was a general book list but, yep, it's technique. Perhaps we should start one on fish ID?