Because species & creatures are among my favourites in the 'SW'-galaxy, I've added another blog entry about them. In the course of the years, there have been many books about species & creatures. I have created two files where you can see in what book a certain species or creature from the movie / spin-offs has appeared.

You can check my previous entries about species & creatures here:
Alien Species
Creatures

I wanted to include the most important books that have species / creatures as their main subject. These books are not the only books where you can find alien species / creatures. I have also included an extra column about 'other appearances'. This is interesting in particular for a couple of species that have never appeared in any book, but have appeared in these other articles / books (Lutrillian & Swokes Swokes for example).

Both documents can be downloaded. Whenever anything changes, I'll update them.
ALIENS
CREATURES

Alien Species: Galaxy Guide 4 - Galaxy Guide 12 - Alien Encounters - Essential Guide to Alien Species - Alien Anthology - Ultimate Alien Anthology - New Essential Guide to Alien Species - Official Databank - Fact Files - Others
Creatures: SW Sourcebook(s) - Essential Guide to Alien Species - Alien Anthology - Wildlife of Star Wars - New Essential Guide to Alien Species - Official Databank - Others

# DARK BLUE = Species / Creature appears in this book.
# LIGHT BLUE = Species / Creature appears as an 'additional' species.
# WHITE = Species / Creature does not appear in this book.
# GREEN = Species / Creature cannot have appeared in this book, because it wasn't part of the SW universe at that time the book was published. I know that some species - for example the Yuvernians - were only recently named, but that doesn't matter. They (Yuvernians) appeared in 'RotJ' and the species could have been incorporated in any book since 1983.
# RED = Species / Creature has not yet been featured in any book.
# ORANGE = Amount of Species / Creatures that appear in this book. I have included species that were added in the 'New Essential Guide to Alien Species' with the additional species because I estimated that their entries contained sufficient information to count as an entry. I did not include additional species from the 1st 'Essential Guide to Alien Species', because they didn't contain enough information.

If we come to conclusions, we can see that the 'The New Essential Guide to Alien Species' and the 'Ultimate Alien Anthology' from 'Wizards of the Coast' contain the most Alien Species from the movies (+/- 90). 'The Wildlife of Star Wars' has the most creatures (although some entries are really short, but all creatures are beautifully illustrated). The Official Databank - as you can see - is also a very decent source.

PS: 'Ultimate Alien Anthology' was published before 'RotS' and 'Wildlife' even before 'AotC' and 'RotS'! That means they covered a lot from the movies that were already released when the books were published.