can these be read out of order and does each book end or leave you hanging? thanks

I wouldn't recommend reading them out of order, personally.

Don't read them out of order.  And they are not cliff hangers. 

You really need to read them in order.  Ditto that they aren't cliffhangers, but the story does build from the last one.

definitely read in order.  as mentioned, not cliffhangers, but they all build on each other.  plus i would guess that in following up on things from earlier books, they'd be significant spoilers for those earlier books if you read them out of order.

I read the 4th (I think) book 1st because I picked it up in the train station when it came out in paperback.  I enjoyed it, but I felt like I was missing a lot.  Eventually, I went back and read them in order, and liked the series a lot more.  I would say that reading them in order definitely makes them better.  It would be especially hard now to start with the latest one and try to follow it.

I don't see how they could be read out of order.  It almost feels like one huge long novel with different episodes.  I've just read #4 through #7 in a row, and it really feels like a continuous story to me.

I am reading that series now and I accidently started reading #6 instead of #5 and, too me, it was noticeable that I had the wrong book in the series.  So, I bought #5.  Lik Matt said, it does seem like a continuous story; one long novel.