Now I'm sure the answer will be 'don't read it its awful' but if I have not finished the DNT or read LOTF can I listen (there are unabridged Audiobooks available) to FOTJ without those prior series, assuming I know some of the spoilers from LOTF?
If you want to read/listen, I'd jump in. Series like Star Wars are also geared to attract new readers. I jumped into the middle of LOTF after a long hiatus, pre-NJO, and I was able to understand everything fine. For what it's worth, I thoroughly enjoyed the series. If you find that you like them, don't mention it in these boards, or the Star Wars opinion police will be sure to let you know how much better and/or more correct their opinions are.
From what I've read, Crucible is 'Meh', but the other two are all right. MF is really connected short stories spanning the Falcon's history - with a bit of a mystery story thrown in. Mercy Kill is great, IMHO, a fitting memorial to Aaron Allston (RIP). Try FotJ from out of the Library, just in case, but otherwise what DarthStymi said, above.
Mercy Kill and Millennium Falcon are a bit deceptive, though - they are really stories set over periods of time that don't require a lot of knowledge about what is happening in modern times. I never finished FOTJ, but it didn't really affect reading Mercy Kill, as long as you had read Allston's Wraith Squadron books.
Mercy Kill I recommend without reservation, it's a good book. However it's light on the starfighter action, amusingly enough. Heavy on the commando front however.
Aside from the "Its an awful series, don't read" advice, you can probably read FotJ by itself. It explains itself mostly, and FotJ's plot isn't too complicated. It does build somewhat on events from LotF, but just general spoilers about the previous series is enough. Even if you did read LotF, it wouldn't help FotJ's plot much anyway. Actually, FotJ might be better on its own since continuity and logic between books, much less different series, is very weak in post-NJO novels. Millennium Falcon isn't an awesome novel, but its still quite decent, being written by Luceno (possibly his weakest novel, but that's still better than most Star Wars novels). Mercy Kill is a better book and fortunately doesn't have much to do with FotJ, though it does reference it and builds on some events that happen there. Crucible is... basically like all of FotJ's flaws compressed into one book. It can be read by itself, it sums up the background well enough, even if the recent history is a bit hard to believe. Better to go read Millennium Falcon and Mercy Kill first though. Or save it for last, whichever.
I didn't know that Mercy Kill ties into FOTJ. That's disappointing as I thought it was a legitimate X-Wing Rogue/Wraith Squadron novel.
It is. It has little to do with the overall plot of FOTJ, and focuses on the fallout of one particular event (that I guess FOTJ didn't bother to do so). More importantly, it shows Wraith Squadron working during the later NR era and during the NJO, with chapter-long flashback sequences.
Yep you can go for all of those without bothering with LOTF or FOTJ, though at least for X-Wing is much more fun if you have read the rest of the X-Wing books.
I started FOTJ but I've decided to finish the DNT and read LOTF before getting the FOTJ Audiobooks, it just feels wrong to jump ahead for the sake of listening to some Audiobooks