Jerevan,
“The Lives of Dax” is a recent paperback novel published by Pocket Books and is set after the end of the Deep Space Nine series. I’m pretty sure that the stories contained within are not canon because, to my knowledge, the only stories considered official are the novelizations of various episodes and movies and “Mosaic”, a Voyager novel chronicling the life of Kathryn Janeway as written by one of the original producers of the television series. (Her name eludes me at the moment, sorry.)
Either way, as an avid reader and owner of most Trek books (I own and have read about 90% of them at last count), I can assure you that the book should be worth a look despite not being recognized as official. But, also, I could be wrong… the past few DS9 novels have all had a continuity unlike most other series.