My family and I often share books, so after reading The Hunger Games I had to wait for my husband to finish Catching Fire.  The thing is, I started reading another book in the meantime and never got around to reading the second.  When the third book came out, I was so excited but had to (obviously) read the second.  I picked the book up on a Wednesday and it was done by Friday evening - it was so captivating.  I am a very busy person so reading a book of that magnitude in that amount of time was impressive (to me anyhow). 
The first thing I want to talk about is the characters.  I love Peeta and Gale - they are genuine, loving, intelligent patient characters.  Peeta is so protective and patient with Katniss.  He knows she has feelings for Gale but doesn't pressure her.  At times he is frustrated and hurt (who wouldn't be) but he always puts Katniss's needs before his own.  Gale is quite similar - only he is a bit pushier than Peeta.  Both characters have become rocks for Katniss, but she finds she cannot maintain her balance standing on both of them.  Katniss, as a character bugs me a bit in this book.  She is not quick to figure things out and I want her to be.  She has been through too much to be naive - one would think - but she maintains her naivety. 
The book is not just its main three characters though.  Readers know a twist is coming so it is no shock that the next Hunger Games takes a shocking turn - previous victors must re-enter the games.  That means Katniss is returning to the arena.  Throughout the book, much foreshadowing occurs for the readers, and Katniss.  Whom to trust or not is constantly in mind.  The end is such a cliffhanger, I find myself glad I waited until after the third book came out to read the second...I don't know how I could have waited months to see what happens next!
Overall then - This is definitely a must read.  Of course, read The Hunger Games first but once you do that I can almost guarantee you are going to want to continue on in this impressive trilogy!