Here is an excellent post from Tim Challies. Please read it before you go out and buy one of the heaven books. An excerpt:
Travelling to heaven and back is where it’s at today. Don Piper spent ninety minutes there and sold four million copies of his account. Colton Burpo doesn’t know how long he was there, but his travel diary has surpassed 6 million copies sold, with a kids’ edition accounting for another half million. Bill Wiese obviously booked his trip on the wrong web site and found himself in hell, which did, well, hellish things to his sales figures. Still, 23 Minutes in Hell sold better than if he had described a journey to, say, Detroit, and he even saw his book hit the bestseller lists for a few weeks. There have been others as well, and together they have established afterlife travel journals as a whole new genre in Christian publishing—a genre that is selling like hotcakes, or Amish fiction, for that.
I’ll grant that the cost of this type of journey is rather steep (you’ve got to die, though only for just a few minutes), but it’s a sound investment when you factor in the sales figures. I can think of quite a few authors who would trade a few minutes of life for 50+ weeks on the bestseller lists and a few appearances on TBN.