Hi ravenmolehil...
I have not read this particular book. I'm not even familiar with Don Piper, except for having seen his name mentioned in an advertisement or article.
I know we shouldn't have knee jerk reactions to such, & just focus on the preaching gospel, but I think his excitement from the book will open a door (that is usually closed) to witness.
I suppose that we shouldn't have a knee-jerk reaction -- but we should be extremely cautious.
After becoming a christian, I read countless books about individuals claiming to have died and gone to Heaven. The main similarity to them is how completely different most of their stories are. There are some that are obviously incorrect. For instance, a particularly famous prosperity preacher/comedian, Jesse Duplantis, claims to have seen "Gucci" furniture [complete with the name tags] in his Heavenly mansion. He also claims to have heard angels playing rock music on heavenly pianos. There are some that are quite suspicious. For instance, Roberts Liardon claimed to have caught a glimpse of Heaven in which he found out that there will be "paying jobs." And then there are some that sound quite credible.
Dr. Richard Eby claimed to have died and gone to Heaven. Later on, he claimed to have caught a glimpse of Hell. He claimed that God specifically told him that he would not die before the Lord's return. He was a frequent guest on TBN. His story was quoted around the world as "proof" that Jesus was coming soon -- particularly when he grew old. However, Dr. Eby died in 2002.
Paul spoke of a nameless man (often thought to be Paul himself) who was "caught up into the third heaven" (or "Paradise"). The ironic thing is that Paul claims that what was seen "is not lawful for a man to utter" (2 Corinthians 12:2-4). There are so many claims being boastfully presented by modern ministers of the Gospel, it is important to remember the caution that Paul used in sharing such a story.
In the end, I would use extreme caution in the embracement of such tales. While I don't pretend to know the validity of any of them, I am quick to include a disclaimer as such. We cannot know the validity of these stories. This doesn't mean that an individual who shares is lying. They may have dreamt of Heaven. They may have had a near-death hallucination of Heaven. And they may have actually seen Heaven. But it would be impossible (outside of the obvious) to know the difference.
:-)