My knowledge of Wilkie Collins comes almost entirely from The Moonstone and The Woman in White. I enjoyed those when I was young, and re-read them several years back. With the advent of e-books and free books, I picked up a lot of Mr. Collins' work (and that of his friend Mr. Dickens). Armadale was my first venture into this unknown territory.
Armadale is a long, convoluted mystery about two men named Allan Armadale, their sons, also conveniently named Allan Armadale, and the woman who links them all together. The first two end badly, and a core query is whether the sons much necessarily end badly - fate, predestination, etc.
The book is long, but I enjoyed almost all of it. I contrast the 600 pages of Armadale with the 600 pages I had remaining in Lawrence Durrell's Alexandria Quartet when I picked up Collins' book. Armadale is certainly less self-consciously 'literary', but it's no shallower, and it's a lot more fun to read.
Collins starts with a fairly defensive foreword warning of experimentation, and leaving judgment to history. I read the book 150 years later, so I guess he wins. At the same time, I'm not quite sure what he was so defensive about. The story is told using all sorts of narrative devices - multiple points of view, letters, journal entries, you name it. Mostly, it works very well. The book also has a number of rants about one or another aspect of society. A number of them are funny, and none of them really get in the way of the story. In fact, the only narrative tic that bothered me was the number of references to "If only this were fiction!"
In terms of story, there's a good range of characters, most of them likeable (the lead Armadale himself is a bit whiny). The plot is not surprising, but Collins sustains the interest well despite the story's length. The question of predestination failed to interest me, but otherwise the story was fun.
All in all, a fun, light story well worth reading.