I've been a fan of the majority of the Stargate Atlantis books, but I'm afraid I can't recommend the legacy series. The first book (Homecoming) is slow and Rodney McKay in particular is out of character. The Lost does not improve the series.
The plot is slow, and the more of the characterisations are poor; now there are sections where Sheppard, as well as McKay, acts strangely. Some dialogue just doesn't have the voice of the character. There are some plot points that are decent, in particular the Genii plot line, but overall the book is far too slow paced.
I am also not a fan of the Sheppard/Teyla ship and this book puts the two characters in a relationship.