English and World literature is a must. Get C.S. Lewis, Tolkien, Dickens, Austen, Melville, Dostoevsky, Tolstoy, Hawthorne, Walter Scott, Sabatini, Dumas, Hugo, Shakespeare, Milton, Balzac, Harding, Thackeray, and Twain. Since you are looking for an heirloom library, I would highly recommend
Easton Press. The books are expensive, but not when you consider how long they will last, and how solidly and beautifully they are made.
I'm guessing Lane was in a hurry when he made that list.
Tolkien's translation of
Pearl is of more importance than any writing by Tolkien himself. This says more for the value of
Pearl than the unimportance of Tolkien, naturally.
If it's an either or, it would be better to leave off some of the novelists in favor of some of the poets (without going back to classic antiquity): Dante; Dryden; Pope; Shelley (you could replace Hawthorne, Thackeray and Balzac, for instance, with no great loss). I would also have thought Flaubert to be of more importance than Dumas.
Sabatini?
Harding?
And there's a lot to add: classics aside (not because they are unimportant, but because they can be taken for granted: a library without Homer, Aeschylus, et al is hardly worthy of the name) there is:
Beowulf; Chaucer; Malory; Spenser; Donne; Addison; Swift; Johnson; Fielding; Sterne; Coleridge; Chesterton; Orwell. There are books you should have for sheer charm value, like the Grossmiths'
The Diary of a Nobody. There are far more than two Russian authors, and I would be so bold as to say that Gogol and Pushkin may be and Chekhov certainly is more rewarding than Tolstoy.
Don Quixote should not be left aside. There are the authoresses: Emily Bronte; Virginia Woolf; Katherine Mansfield; Kate Chopin. There are people from whose larger work perhaps one book emerges as worth preserving, as seems to me to be the case with Edith Wharton, the book in question being
Ethan Frome, or perhaps (translation work on the
Bestiary not being taken into account) T.H. White with
The Once and Future King (
with The Book of Merlyn.
And then there are people who are relatively minor and unknown, yet whose absence would be a real loss, such as Arthur Lindsay Gordon. And there are authors against whom there is something of a stigma, like Kipling (in part deserved, think of
If and the jingoism), whom are yet tremendously worthwhile.
The period in between the world wars was rather insanely fertile: to be sure, much of what was produced was not of remarkable
tendency if one regards its heirs: but the achievements of Joyce, of Lawrence, of Huxley, of Russell, even of Eliot are themselves worth preserving, whatever malformed moon children they may have spawned.
And we haven't even come to the abundant ground of children's books: Carroll, Nesbit, Potter, Marshall, Barrie, Milne....