I have some preliminary thoughts to kick off a discussion. One thing that stands out structurally in the book is that it features contrasts. For example, the lonely and grotesque death scene of Mrs. Proudie contrasts with the sweet leave-taking of Mr. Harding. Similarly, the heartfelt love affairs of Barset folk (Henry and Grace, John and Lily) vs. the heartless play of the London affairs (Conway Dalrynple and Mrs. Dobbs Broughton, or, alas, John and Madalina). Generally, there is a marked contrast between the sincerity of the country characters as opposed to the brittle artificiality associated with London.
It is interesting to me that Trollope, who features the Marriage Plot prominently in both Dr. Thorne and Framley Parsonage is content to leave Lily and Johnny divided, apparently never to unite. It occurred to me in TLCoB, however, that Johnny really isn't worthy of her. In The Small House at Allington, we were inclined to forgive Johnny in his na´vetÚ for is entanglement with Amelia Roper. But his dalliance with Madalina Demolines shows a fundamental lack of sincerity that results in the reader (this reader, anyway) being inclined to agree with Lily. Johnny is a very likable young man, but he is no longer a suitable match for Lily. In the novel, he is the structural link between the Barset scenes and the London scenes. It is also true, in my opinion, that London has corrupted Johnny to the extent that the sweet young man of TSHaA, who would have been a natural match for Lily, is no longer an appropriate partner. If she had never met Crosbie and accepted Johnny when he was still a hobbledehoy, he would have grown up straight and true. But alas, she did not. Now, he is no longer so solid.
Trollope takes an immense risk in hanging his whole novel on Mr. Crawley and then making him so fundamentally unlikeable. I wanted him to be found innocent, of course, but I confess that I never warmed up to him, even at the end. If anyone were to wonder why "Pride" is considered a Deadly Sin, especially in this age of concern over Low Self-Esteem, I would immediately direct them to this novel. Crawley's pride in his intellectual prowess, his moral spotlessness, and, oddly, in his poverty is quite off-putting. I must confess, however, that I truly enjoyed his giving Mrs. Proudie what she deserved. (Kudos to Dr. Tempset as well.)
I guess that's enough for now. Please share your thoughts, Guillermo.