This book was tortuous for me to get through. At first I was able to accept the "flowery" language as that of the time, and I was intrigued by the opening chapter where the Cumaean Sibyl's cave played a part (I have studied the Sibyl's and like any reference to them). I also wanted to give it a chance since I loved Frankenstein by Shelley.
Shelley was prescient about a worldwide "pestilence" or even as she named it once, a "pandemic." There was a lot of aimless wanderings in trying to get away from the "plague" but some of the reasoning behind the destinations didn't make sense. The stilted language kept me at an emotional distance from the characters until close to the end of the book.
I plowed through to the bitter end, with the expected outcome being the "Last Man" (to survive) of course.
Lots of philosophizing, many adjectives, and lots of people dying or dead.
If you had lots of time to only read this one book and didn't have a bookshelf full of new books waiting to be read, or if you are studying the writing of this time period, have at it!