Codex by Les Grossman
This twas an intriguing book - not of my usual 'genre' but interesting none the less (the cover art caught my attention.
Edward is a private financer and on his 2 weeks break from transferring from his office in US to London he takes up a job from one of his employers - but soon finds himself in the middle of something much larger than cleaning and cataloguing an old library. Not only that but Edward, not the gaming type, finds himself constantly playing MOMUS - and really badly at that.
Things start to go a little strange when he tries to search for a particular book and is strangely told not to continue with his work - sensing something amiss Edward continues with the help of the smart but bookish Margret and they find something extraordinary.

It was a good read I thoughly enjoyed it - worth taking a look at if you can find it.