How to tell whether an adult would like these books?
1 Do you like action books / action movies with pacy plots? 2 ... even if there is no characterisation or emotional depth? 3 Would you like a book that has a lot banter in it, but also has a dry humour running all the way through?
If you said 'yes' three times, I think you would like the book. Even one 'no' and I'm not so sure. I loved it.
It has a pacy plot. Think Jason Bourne, James Bond, Batman movies, Die Hard. Like these examples, it has very little characterisation.
It's got a lot of humour, though sometimes the banter gets a bit much. It reminded me of Terry Pratchett, but lighter. Artemis Fowl, the 12 year old criminal mastermind, is part James Bond, part James Bond villain, with a little pinch of mafia godfather. He is ridiculously clever, in an entertaining way, motivated by money again in an entertaining way, but endearing too.
Other reviewers argue whether it is or is not like Harry Potter. I think it's nothing like HP. More like part Robert Ludlum (the author of Jason Bourne), part Terry Pratchett (drier humour, but not as fantastically weird as TP).
It does have goblins, elves and dwarves in it, but don't let that put you off - it's an action book in a fantasy setting, rather than a fantasy book (in my view).
For an adult, it's a light read (Waterstones had it in the 9-12 year old section), but a fun way of filling a few hours.