I saw the show at the weekend and bought this CD at the theatre. Yes, it is a reissue with two extra tracks, but they are hardly being discrete about it: it's written across the front of the CD.
I was pleased to be able to get this as the only copy I have of the 1991 version is on cassette, which is not much use these days. The 1991 cast were amazing (although I do think Lee was better than Jason) and this CD doesn't disappoint.
For those who are complaining, I'm afraid this is the way cast recordings are going these days. For example when a show opens here after having played on Broadway then it is rare to get a London Cast recording (see Wicked, Spamalot, and Avenue Q as recent examples). Given that the current production of Joseph is identical to the 1991 production (with the exception of a new song, which is one of the two bonus tracks on this reissue) right down to the staging, set, and costumes, then a new recording was obviously not thought worthwhile and/or fiancially viable.
Do buy this album, just be aware that it is a reissue and you will not be disappointed.