Size 12 is Not Fat reminds me a lot of the Confessions of a Shopaholic series or the Deadly Cool series because it's just a lot of fun. Though Heather, Becky and Hartley are so totally different. 
 I want to be BFF's with Heather. She has her faults but she is fun and caring and fairly grounded for being a former pop star. She did crazy things, all because she cared and was always willing to go that extra step. I also really enjoyed how she worked out what happened ("girls just don't elevator surf") it sounds completely illogical, but right at the same time. She is one of my new favorite characters. 
 Meg Cabot really made me feel like I was Heather. I was fully engaged and I loved Heather's thoughts regarding pretty much everything. She was just a real pleasure. 
 Heather ex-boyfriend, Jordan, is still a pop star (of a boy band of course), and pretty much just how you would picture a pop star. He's arrogant and believes the world revolves around him. And of course, everyone should just fall in line with what he wants. 
 Heather is living in the apartment above Jordan's brother Cooper. Whom of course she is attracted too, but he doesn't notice her that way. I adored Cooper. He's pretty well put together but has a little mystery to him too. Plus he pretty much gave the finger to his family (Jordan, and their father, who runs the record company) because he didn't want to be in the boy band (which was a wise choice). 
 I also really liked Heather's friends, Magda and Patty, who are so completely different. Magda is... unique and Patty, while normal, leads an extravagant lifestyle because of her husband. 
 While I do like romance in books, its always nice to read one that doesn't have a romance (though Heather is totally crushing on Cooper). 
 I really enjoyed the mystery. I figured it out about 2 pages before it was made known in the book so I was kept on my toes throughout most of the book. 
 I know that this is going to sound strange but I really liked that Heather doesn't have gobs of money. All too often the main characters always seem to have an unlimited supply of funds either because they are rich or because it's just not ever really brought up. I get why authors do that but it's nice that you don't see Heather doing anything and everything.