19 hours ago, Jens H said:

The “bible” of nudibranchs. Here you will find almost everything you need to know about nudibranchs that you might encounter underwater. Unfortunately currently out of stock, try to get a used copy or a PDF:

Nudibranchs of the World (Debelius, Kuiter), ISBN 978-3939767060.

Nice book on creatures you see during muck diving. However, it is still not complete -that would be mission impossible:

Muck Diving: A Diver's Guide to the Wonderful World of Critters (Nigel Marsh), ISBN 978-1921517815

I have a copy of this book, I have been told there are some inaccuracies in it, I think from one of the Nudibranch ID facebok groups and also that a lot of species have changed names like all the Chromodoris sp. that are now Goniobranchis for example. I still use to get a starting point and cross check by googling the species name.

23 hours ago, Jens H said:

The “bible” of nudibranchs. Here you will find almost everything you need to know about nudibranchs that you might encounter underwater. Unfortunately currently out of stock, try to get a used copy or a PDF:

Nudibranchs of the World (Debelius, Kuiter), ISBN 978-3939767060.

There's one on Abebooks for 463 USD 😱