I know I use cool and awesome way too much - but honestly, the Demonomicon is just that. Awesome. I have no qualms rating it as the best supplement book of 4e, a spot that Underdark held previously (in my mind, of course).
Well, I'm not yet even half-way through the book (just finished reading the layer descriptions), but so far I am underwhelmed. In particular I noticed something really annoying:
Blatant use of copy and paste.
Time and again when reading a new section, I got this strange feeling of deja vu: "didn't I just read exactly the same thing, a while ago?" And it's not just a feeling, it's very real. E.g. information in the general description of a layer is repeated in later sections (sidebars, locations, inhabitants) with little or no alteration. There's no additional information - it's just reworded, and sometimes not even that!
Check out page 64, the last three sentences of the History section. Now compare them to page 65 'The Eye of Veshoriak', second paragraph. The sentences are repeated
verbatim, except for a bracketed insert '(see Monster Manual, page 52)'.
Even more annoying: There are sections that are almost identical even though they describe _different_ places!
Compare page 47 'Bastion of Skycleave' with page 61 'Tornbend and Skyshrine'. Both describe earth motes anchored to the ground with big chains using (almost) identical words.
I'm getting the impression I may lack the 'nerves of steel' required to enjoy reading the book.
To me this looks like the authors ran out of time and/or ideas. That's not an issue I noticed when reading 'Underdark' or 'Plane Below' (the latter being my favorite 4e book so far).
Another issue I have are the maps: The show quite a few locations that aren't mentioned anywhere, while there a descriptions of places that are _not_ on the maps.
Could it be that these maps are reprints? E.g. from the 3e Codex where more (or different) locations have been described?
I really hope the book gets better in the second half.