The Naughty List by Suzanne Young

From Amazon: As if being a purrfect cheerleader isn’t enough responsibility! Tessa Crimson’s the sweet and spunky leader of the SOS (Society of Smitten Kittens), a cheer squad–turned–spy society dedicated to bringing dastardly boyfriends to justice, one cheater at a time. Boyfriend-busting wouldn’t be so bad . . . except that so far, every suspect on the Naughty List has been proven 100% guilty!
When Tessa’s own boyfriend shows up on the List, she turns her sleuthing skills on him. Is Aiden just as naughty as all the rest, or will Tessa’s sneaky ways end in catastrophe?
The Naughty List. Is your boyfriend on it?

I found this one really cute and really good fun. It felt really fresh and original - although I'm not sure how believable I found the SOS part of the story I really loved it and found it an excellent premise for a series.

I loved Tessa's voice and can't wait to spend more time with her in future installments. I loved her perky attitude and aversion to swear words - some of the things she said (or thought) instead made me laugh out loud. I also really loved her relationship with Aiden. I completely adored him and thought he was really sweet and a great match for Tessa.

I found the story really gripping and didn't find it predictable. I wasn't sure what was going to happen and the ending surprised me - I really liked it and it sets up the next book nicely.

I hope there are many more of these books to come - I have preordered the next two already and can't wait to read them.