When it comes to aspirational reading — those books we think we should read but never get around to cracking open — many people think of epic novels like “War and Peace” or “Infinite Jest.” But those two doorstoppers are still no match, at least in terms of length, for Samuel Richardson’s “Clarissa: Or The History of a Young Lady.” That 1748 classic, at 1,494 pages (a variety of appendixes in my edition, including a page of relevant sheet music, round the whole thing out to 1,534 pages), is, by most measures, the longest English-language novel in a single volume. As Judith Pascoe, an English professor at Florida State University who has studied and taught “Clarissa,” says, “Once you’ve read it, you join a fairly small club of other people who’ve made it all the way through.”