That book is the essential tome.
I try each year to watch as many Unis as I can stomach but after the initial wave of classics and the fresh start in 1939, they really peter out in quality very quickly.
The Old Dark House is a classic, should be fully restored and represented to the public in all its glory. It is pure Whale and glorious for being so. Kino's DVD is sourced from a LD master of a worn 16mm reduction and just pitiful.
The most underrated is Son of Frankenstein, a classic in its own right. This singlehandedly jump-started the second wave of Uni horrors.
For my money the only ones really worth anything are:
Dracula, Spanish version, Frankenstein, Bride, Son, TODH, The Mummy, Mummy's Hand, Invisible Man, Invisible Man Returns, Invisible Agent, Phantom '25, Man Who Laughs, Wolf Man, F. Meets the WM and Creature.
The rest can still have their charm but drag on, even the quickie hour long bottom bill fillers. When the new studio heads decided these would be cheap programmers it signaled the end of the horror film's prominence. The lesser films can have their moments, but are not very good. Like turning Karloff's tragic Imhotep into the pathetic Kharis. (Though I love Hand, Chaney's mummy is just awful.)
The non-monster ones really feel more B-picture. The Karloff and Lugosi starrers are made by their stars and not so much the story. The Black Cat works because of the atmosphere and star turns. It was cut to ribbons which damages the narrative terribly. The Raven is terribly silly but again made by the star turns. Otherwise the rest start to decline in quality terribly.
I like to have my brain stimulated in horrors. Not jump scares, which are stupid and pathetic. The problem is that only a few Unis were made by Whale, Freund, or even a Rowland V. Lee. After their quality left it was only in the few great horrors pre-Curse of Frankenstein that anything worthwhile happened. And Hammer had the same problem of quality lessening over time, due to studio desires to make program filler and increase profit margins with talent leaving over time.
This just made me think, you know Night of the Demon cannot be praised enough. For all the discussion Cat People generates Demon is an unbelievably good picture.