Review of Transition by Ian Banks

A novel set in the multiverse, with characters who are aware of and can travel between parallel universes. It's nicely done (or perhaps nicely overdone, since quite a lot of the descriptions are sort of camp in the way that steampunk sometimes is - especially the lavish settings and costumes of Madame d'Ortolan, who functions as a principal villain). 

Lots of drugs, some sex, not much rock and roll.

It took me a little while to get into it, but I ended up enjoying it and was almost sorry when it ended.