Here are a few ideas for your consideration:

The Quincunx, by Charles Palliser – a big complex Dickensian multiple mystery dense with atmosphere, gothic flourishes and a truly puzzling plot that is a blast to figure out. His The Unburied is also really good although about half as long, if you’d rather have something shorter. Also in the same universe is The Dress Lodger, by Sheri Holman. Another densely detailed Victorian mystery – grim and grisly fun. Or you could return to the source and read Wilkie Collins' The Woman in White. Just to throw out a few more in this vein. Ex Libris, by Ross King, The Syracuse Codex, by Jim Nisbet.

Mr. White’s Confession, by Robert Clark. This depression era literary mystery about a photographer who seems the perfect suspect for a series of murders will have you guessing until the very end, and then you’ll want to talk about it to compare notes. Beautifully written, surprising, and curious.

Zeitgest, by Bruce Sterling. Wild jam-packed funny thrilling hypersmart thing, circa Y2K, and on a par w/ Robbins & Stephenson. Also Jack Womack’s Let’s Put the Future Behind Us.

American Gods, by Neil Gaiman. The old gods never died – they’ve just gone into hiding, but now a new race of American gods – television, credit, internet, plastic – are taking over, and the old gods make their stand. Rollicking, thoughtful, fun. (Which reminds me of The Minotaur Takes a Cigarette Break, by Steven Sherrill. The minotaur is working in a rib shack, trying to live a normal life and find love outside the labyrinth) Likewise, you might enjoy James Morrow’s Towing Jehovah, about what happens when the corpse of god (who is dead, or hadn’t you heard) lands on earth. Morrow is smart and irreverent and fun to read – it is the first of a trilogy.

Oh Pure and Radiant Heart, by Lydia Millet. A librarian starts a world peace cult three famous nuclear physicists who have travelled from the past. It sounds hokier than it is – what it is, is brilliant and moving and fascinating.

(I recently suggested to another reader Dan Simmons’ The Terror and Kathryn Davis’ The Thin Place, and think you two just might like those as well).