Several possible approaches come to mind. One is that a timeline of assorted events will be included with a "pick a point" caption. Another is that the initial game world will be set initially at a specific point in the chronology (probably between Dead Beat and Proven Guilty or just after Proven Guilty) and then updated after each book for those who wish to keep current. Most likely is that the gap of years between books will be taken advantage of to set things in.