Codex

An investment banker finally has a vacation. However, he is asked to visit a client he helped with. He ends up being drawn into a minor task with some old books that he thinks is below him. However, he keeps coming back. He also gets an open source CD game from a friend that seems hyper-realistic. The description of the game dates the book. It is on a CD-ROM and he is impressed with the "realism". He eventually discovers a student of medieval books who helps him to find the missing "codex" from an obscure writer. They go through many adventures. Through his friends, he learns that the nobles he is working for are crazy rich. He also learns there is some conflict between the spouses. The codex may have a clue unraveling their relationship. He discovers a relationship between the game and the codex (influenced by an easter egg in the video game, created by an engineer that had previously discovered the codex.) He also begins to doubt his life choices and ends the book in ambiguous circumstances with a whole lot of money.
The book is paced nicely, but largely forgettable. There are some "thriller" aspects to it, though it is more about a young adult coming to terms with his life choices.