There's been a lot written about Losing the Signal and I won't duplicate what available elsewhere. I would definitely recommend the book. Whenever I read anything related to the Waterloo tech scene of the 1990s and 2000s, I expect to spend a lot of time rolling my eyes and muttering comments to myself, but that didn't happen here. (I have some minor quibbles, but you'll always have those.)
I followed RIM closely from about 1995 to 2010 and enjoyed that part of the book primarily for the retrospective quotes from people who were involved with the company—as insiders, partners, customers and others. And then I pretty much stopped following the company cold turkey in the fall of 2010, and continued to enjoy that part of the book for details I wasn't familiar with (beyond what you couldn't have missed in headlines), which tells me that you don't have to know a lot about RIM to appreciate the book.
You can't cover everything in a book, and I thought the authors made good choices about what to include. It focuses on the Mike Lazaridis-Jim Balsillie era (and relationship) and quickly goes over the subsequent Thorsten Heins period. You'll read about Barenaked Ladies and U2 but no mention of Alicia Keys.
I did think that Com Dev got short shrift. It's briefly mentioned in two out-of-sync spots, but Com Dev was RIM's largest shareholder for years—owned more of the company than Lazaridis. Com Dev's pre-IPO shareholders wisely kept ownership of their RIM shares when Com Dev went public in 1996 but ended up selling millions of dollars worth of shares—at a price nearly as low as RIM shares ever got—when Com Dev badly needed some cash. It was very controversial and I would have been interested to read current comments from surviving senior Com Dev execs about their relationship with RIM.
I was interested to read that RIM's infamous options backdating episode was a big deal to Lazaridis and added to the rift with Balsillie. I had a hard time seeing that whole incident as more than a dog-and-pony show ... which is easier to say from the comfort and safety of my office, but it all came across as regulatory theatre with Balsillie as the main sacrificial lamb. And even that didn't seem like much of a sacrifice. He received a hefty fine, but relative to net worth, it really wasn't that much (again, easy for me to say). But the book describes how the situation weighed heavily on Lazaridis in particular, and that was a surprise.
At the same time, I didn't think the backdating issue was well covered in the book. The authors write that "together, the CEOs and [CFO] Kavelman agreed to pay the [Ontario Securities] commission a combined $83 million", but that money was actually what they agreed to pay RIM (the additional fines were about $9 million, with Balsillie paying nearly two-thirds of the total). And the $83 million could be paid by forfeiting options—that was all part of the show. RIM and, by extension, its shareholders weren't the perpetrators of the backdating, they were the supposed victims.
You won't get a feel for how much of an outlier RIM was at its peak among Canadian tech companies, but that's more of a personal interest of mine than something that needed to be covered (as I've said before, a lot of government support for the tech business ecosystem in Canada over the last several years had its foundation in the quixotic expectation of finding "the next RIM" ... and now that it hasn't happened, that ecosystem is increasingly being seen as a failure).
What you do get is a respectful, but not fawning, portrait of Lazaridis and Balsillie (a previous book on the subject—which I never read—was said by some reviewers to be too adulatory ... which would be difficult to write in 2015, but not at all in 2010). And, from talking to former RIM employees over the years, it felt to me that the book did a good job of capturing how chaotic things could be behind the curtain.