ColumbineEverything you think you know about the Trench Coat Mafia is wrong—unless you’ve read this clear-eyed examination of the 1999 massacre.

It explains why the earliest reports were flawed and why the media were so quick to craft a narrative that the world was ready to ingest. The truth takes patience, which Dave Cullen demonstrated in the 10 painstaking years he took to complete Columbine. Released in 2009, its relevance has only grown, as school shootings have become a gruesome part of this nation’s experience. Teachers and students make up a big percentage of Columbine’s readership, and Cullen has visited both Harvard and Yale for in-depth book discussions.

To accommodate the vast amount of teachers at the high school and college level offering the book as a summer reading list choice or as part of a humanities curriculum, Cullen has recently completed a teacher-and-student guide.

“I have the feeling it’s a win-win for some teachers,” he tells the Press. “[Teachers] are always looking for books that will help the kids, but especially that the kids will read! And every teacher tells me that happens, once they start… I’ve taught classes and know how much work is involved in writing a new unit/lesson, whatever. A new book means coming up with all sorts of material. But hopefully I’ve already done most of that for them—and have links to everything imaginable to fill in the gaps.” Discover—or rediscover—Columbine.