I have just finished reading the above sequel and thought it was enjoyable. The story is mainly about Darcy and Elizabeth and Charlotte Collins though the other characters of P & P are mentioned, at first I had to get used the fact that Lizzy calls Darcy by the name of Robert rather than Fitzwilliam.
I enjoyed what happens with Mr Collins he arrives at Pemberley with a terrible chill and is confind to bed for the whole of christmas and new year so Charlotte makes friends with Phillip Aston a widower friend of Darcy's. We learn later on that Mr Collins due to his illness has put on weight and Lady Catherine makes him ware stays ones that squeak as well, which I found most entertaining imagining Mr Collins dancing with them on and squeaking at the same time it would be hilarious fun.
Lady Catherine is as obnoxious as usual but in the end gets her due because she gets cast off by Darcy for trying to interfer with his marriage. Towards the end of the book Mr Collins dies of consumption and Charlotte is free to marry again. Due to not being a purist for JA I found this book to be a excellent read and extreamly funny in places.