Just buy it.
While there is a case to be made for non-photographers testing new hardware – after all you don’t have to be Annie Liebovitz to stick a camera on a tripod and shoot a test chart – no such argument can be sustained when it comes to writing software instruction books.
The hardware case is exemplified by sites like DPReview. Many do a good job of explaining and comparing features and performance, while attended by the worst photography on the planet. None of this is helped by a commentariat frequently focused on flame wars over brand X versus brand Y. But, as long as you stay away from the noise passing as commentary, sites like DPR add value to the hardware decision.
On the software front you have many poseurs passing as experts with one common attribute. That is, they seem to be software gurus who grew up with Photoshop and think that their familiarity with the arcana of vector based rendering makes them Cartier-Bresson’s peer.
That is why it is so easy to recommend Martin Evening’s latest Lightroom book, which addresses Lightroom 4. He is a working professional photographer, a good one at that, writes clearly and illustrates his recommendations thoroughly. I have previously bought his LR v2 and v3 and PS CS5 books, and recommend the latest unreservedly. The section on the use of the new enhanced localized adjustment tools alone is worth the price. Mine ran me $30 at Amazon US.
Having bought v2 in paperback and v3 in the Kindle version for the iPad, I find I much prefer the paperback for ease of cross reference and quick access to features I need to understand. At least I don’t have to recycle v3 – the Delete button being all that is needed.