If profanity offends you, don't pick up this book. If scenes of graphic torture by the Christian sect offend you, don't pick up this book. If realistic scenes of humans at their worst offend you, then please, don't pick up this book.
Though this is a book based on the end times as foretold by the Christian bible, it's not one I'd recommend for the true believer, especially if you think Christians are kind, gentle and righteous in all situations. That said, this is the kind of book you either love or hate, I happen to love it myself.
Being an atheist I can relate to the book's protagonist, Jimmy, a non-believer who sees the Rapture take his girlfriend, family and friends and who though makes to the fabled Petra himself is disgusted by his fellow escapees. Given an opportunity to rescue an old girlfriend from what used to be Chicago, USA, Jimmy decides to forfeit his guaranteed entrance to Heaven and takes the "mark" to insure safe passage on a prison ship and leaves behind Petra and its security.
*Jimmy uses the F word A LOT, but it fits his character, the modern setting and the dire situations he endures. This book is graphic, intense, and a read I won't soon forget.