I think I'm going to stop expecting anything from these P&P spinoffs because whenever I do, I'm inevitably disappointed.
Alright, the concept is interesting enough: a semi-retelling of P&P through the eyes of Mr. Darcy. The problem with this book, at least to me, was not that it went beyond the scope of the original novel (I actually don't mind that at all). My problem was that its portrayal of these previously unexplored events was unconvincing.
Like other reviewers, I found this book's depiction of Darcy's parents as cold and unfeeling people to be inconsistent with Darcy's regard for them (as evidenced by Darcy's willingness to honor his father's wishes for Wickham). I also had problems with the punctuation used throughout this book. Punctuation, you ask? Yes. Darcy writes repeatedly with the use of exclamation points, and comes off more like an excited schoolboy than the mature, reserved person we know him to be. Although this is to be expected early on (his first journal entry is when he is only 10), I'd expect his reserved character to come through at least in his later years. No such luck. The writing never progresses beyond the 10 year-old-boy level. Even as an adult, his journal entries continue to be repeatedly filled with statements like, "I love her! She's beautiful! How happy I am!" Enough already! :-) I expect Darcy's writing to be moving and elegant, not excitable and childish.
The book also goes beyond the P&P timeframe by covering events past the wedding. Again, I don't have a problem with that per se. I like to see what happens to the Darcys afterwards. They are portrayed here as happy, passionate people, which is great. However, the repeated use of exclamation points continued to annoy me and I found myself rushing through this last part of the book just to finish up the darn thing. If you don't want to expand on the P&P timeframe, this might be another annoying thing about this book. If you do want to know what happens to Darcy and Lizzy afterwards, I suggest reading the Bar Sinister. It's risque to be sure, but it's also fun and amusing--definitely a much better continuation of the Darcys' love affair than this excitable schoolboy version.
I've been told a much better version of Darcy's story exists. It is called "The Confession of Fitzwilliam Darcy" by Mary Street. Unfortunately, it's out of print and hard to get your hands on a copy. However, if you really want to read something that's actually good, I suggest holding out until you do find a copy. If however, you just can't get enough of P&P spinoffs, I'd suggest reading the Bar Sinister first (assuming you're not a purist--if you are, then read Letters from Pemberley). If you've read both and are desparate to get more (as I was), I suppose this will do (just don't expect anything). However, no matter how desperate you get, avoid at all costs anything by Emma Tennant, or you'll just end up being resentful (I think she's universally hated by P&P loyalists). Have fun reading, but consider yourself warned...