The Beautiful And Damned is longer.
Tender Is The Night centres on the Divers, Dick & Nicole. At the start of the novel they are a relatively recently married young couple holidaying in Europe (unlike any of his other novels, almost none of Tender Is The Night occurs in America). They are the centre of a social circle there, including our initial POV character, Rosemary, a young actress. One of the differences between Tender Is The Night and most other Fitzgerald novels is that the perspective from which we get the story changes regularly - mostly it's from Dick's, but other views are also given to fill in both story and character details. After the initial section, following the Divers and their friends, lovers and other acquaintances, we jump back in time to the beginning of their relationship, before moving to later (around five years after the first section) as their marriage falls apart.
While The Great Gatsby obviously remains Fitzgerald's most famous novel, I know that some hold Tender Is The Night in higher esteem. Yet for me it simply didn't hang together as well as his earlier novels. Certainly more mature, and perhaps an insight into the sort of books Fitzgerald would have written had he lived & written for a longer time (although The Last Tycoon is clearly going to be a better indication of that), but Tender Is The Night also seems lifeless compared to anything up to & including Gatsby. The shifting timeframes and perspectives help keep things interesting, and of course he remains a beautiful writer, but Tender Is The Night never grabbed me in the way that his other books have. Perhaps this is as much my fault as his - and I will definitely revisit it in the future to see if my opinion shifts - but I found less to love in this polished, mature work than I did in his somewhat-flawed first books. Part of the problem is Dick, for whom I never got much of a feel. Perhaps less-obviously autobiographical than some of this other main characters, possibly Fitzgerald never quite figured him out either. There are still some wonderful scenes, and the final section is quite effective, but Tender Is The Night was a bit of a disappointment for me considering Fitzgerald's tremendous talents.