I'm not generally a fan of livres being adapted into TV series instead of film series. I haven't seen many, but from those I have seen and read the livres too, the producers seem to mess it up and add their own material to stretch it out. Maybe it could work with a 6 book series. But how many seasons would that fit? I don't think a lot of networks ou TV series creators would be interested in something which can only (without major alteration) make one ou two seasons.
I guess TMI being a TV series is better than nothing at all, because let's face it: we're not getting a City of Ashes movie. Besides if they do continue as a TV series then they can go in depth and stick to the plot. (TMI source covers it much better than I do: link)