I've been kind of systematically reading or re-reading book series for some months now.
Series that I've read everything available in in the last six months or so:
Walter Mosley's Easy Rawlins series. That's ten novels and a book of short stories; the opening book is Devil in a Blue Dress, which was made into a movie with Denzel Washington.
Janet Evanovich's Stephanie Plum series. Have read everything but the newest (Finger Lickin Fifteen), and have skyrocketed on the library wait list for that one from 682 to 543---not bad for a book that's only been out a week or so. Because of the occasional additional book, this series is not fifteen books, as you might think, but 19.
Tony Hillerman's Jim Chee/Joe Leaphorn books. I wish there were a pile of these backed up, waiting to be published, but it doesn't appear that it's so.
Ariana Franklin's Adelia Aguilar series. So far still a distinctly short series---three books---but the idea of merging a female forensics specialist---if you can call anybody in medieval times a "forensics specialist"---with Plantagenet England is interesting if improbable.
Christopher Fowler's Bryant & May series: Six distinctly quirky books.
Jim Butcher's Harry Dresden series: I've not seen any of the televised Dresden bits, just the books, but they have my attention. Just noticed that the most recent book has come out since I finished reading the series, so have requested it from the library.
Jess Lourey's Mira James series: another infant series--only four books---but interesting so far.
Carola Dunn's Daisy Dalrymple books....
Vicki Lane's Elizabeth Goodweather books. Only four of them, but definitely reminiscent of Sharyn McCrumb's writing.
Terence Faherty's Scott Elliott series. Only four books, and came to this by accident, being familiar with his Owen Keane books.
Bill Crider's Sheriff Dan Rhodes series, a series I really love and wish there was more of...
And venturing from mystery to fantasy, been rereading Robert Asprin's Myth books.
Good reads all, and always actively collecting "where to go next" from here....