Some of my favorite light reading are the thrillers of Barry Eisler. As he's gone along, the overlaps in his characters/series have become more complicated. So, in a fit of OCD and with a nod to the Terry Pratchett Reading Order guide, I made this chart. I offer it here for the edification of all and sundry. But do take the compiler's note about how you can start anywhere seriously.
Incidentally, I got into this because I had just bought my aunt the second Livia Lone book as a present — she'd liked the first — and was trying to think of how to explain who Dox was and how he fits in. It's tricky!