You're probably better off with locality-specific books, especially
for a place like Hawaii with such a large number of endemic species.
Humann has one for Baja and for the US West Coast.

You can buy an astonishing array of local marine life books in Hawaii (not a
surprise, but true nonetheless).  I got mine at Dive shops and at the
botanical garden near Poipu on Kauai.

I came back with 2 excellent guides:

Hawai'i's Sea Creatures, A guide to Hawai'i's marine invertebrates, by John
P Hoover.  1998. ISBN 1-56647-220-2. 366 pages of glossy photos of the
critters of Hawaii, from coral to crabs, nudibranchs & octopus. It gives the
Hawaiian name for some of the creatures.  It's not good at marking the
endemics, but is a good guide to what you can see.  My paperback copy cost
me $24 in Hawaii in 1999. (I don't keep fanatical records--the price tags
are still on  :-)

Hawaii's Fishes, A guide for snorkelers and divers and aquarists, by John P
Hoover. 1993. ISBN 1-56647-001-3. 188 pages of glossy photos of fish. The
endemics are clearly  marked and Hawaiian names are given for many.  An
excellent book!  My paperback edition cost me $17 in Hawaii in 1999.

You can still purchase both of these books, and other Hawaiian topics, from
the publisher:  http://www.mutualpublishing.com/catresult.aspx?categoryID=14

The prices haven't even gone up--the actual prices on the web site are a few
cents less than what I paid, but then, I didn't have to cart them TO Hawaii.

Becky