I've come late to the Tom Holt party, but I'm glad I finally made it. The Portable Door is the first book of his that I have read and I definitely intend to try more.
It is the story of Paul Carpenter, and how he takes a mysterious job in a mysterious firm where mysterious goings-on occur. I found it always interesting, a nice quick read and lightly humourous. I wouldn't say there were many laugh out loud moments, but I chuckled more than once or twice!
I think one of my favourite passages can best sum up the wit and wryly weird writing that Tom Holt employs: "There's this to be said for being hungover; if you've got a job to do that involves substantial levels of ambient weirdness, it helps, because you can't be bothered to notice stuff that under other circumstances would come close to frying your synapses. Treasure maps; Czarist bonds; a case of stuffed dodos; Scarlett O'Hara's birth certificate; two flattened and deformed silver bullet heads in an old matchbox; Baedeker's guide to Atlantis (seventeenth edition, 1902); the autograph score of Schubert's Unfinished Symphony with Das Ende written neatly at the foot of the last page; three boxes of moon rocks...." and so it continues in this vein.
I enjoyed the fact that Tom Holt is clever in his writing and assumes that you, too, must be clever because the vocabulary used is superb and had me scratching my head a few times.
The characterisation is brief but effective - through simple repetition we know that Paul is a bit of a loser, but with a good heart, while Sophie is a prickly but ultimately likeable character. The various partners of the firm they join are wildly entertaining.
My main criticism is with the pacing of the book. The first half of it went fairly slowly, as befits the unfolding of a mystery, but the last third was breathlessly fast and tied up very neatly.
Other than that, this was a fine book and I look forward to more of Holt's work.