The Warden is brief, gentle , and interesting. It actually poses a knotty ethical problem that remains fully applicable to this day (and perhaps always will). I enjoyed it, although I thought it a minor work. In my opinion, it would not really be worth reading except that it provides an introduction to Barchester Towers. While the essential plot points are quickly summarized in BT, I believe that the latter novel would be considerably less enjoyable without first making the acquaintance of (and learning the character of) several of the major players in the latter novel.
I am finding Barchester Towers to be one of the funniest Victorian novels I've ever read. It's peculiar to me that in the 18th-century English novel, I much prefer the humorous ones (Fielding, Sterne, Smollett) to the serious ones (Richardson, for example). (It's odd to me because generally I'm not a fan of comedy in other areas. I don't read humorous contemporary fiction, or watch television sitcoms, or select so-called funny movies, etc.) Austen is also very funny in the transitional period of the Regency. But the Victorian novel is not nearly so funny. The Pickwick Papers is surely a comic novel, but I don't think of Dickens as primarily a comic novelist. He sometimes makes me smile, but I actually have laughed out loud reading Barchester Towers. Similarly, the satire in Thackeray may produce a smile, but I don't recall him as being all that funny. At least not compared to Fielding or Sterne. Eliot, the Brontės, Hardy--fine novelists, but scarcely a smile in the bunch.
I understand that Trollope himself abandoned comedy following Barchester Towers. if so, that's a shame.