"The Fellowship of the Ring is at least as good as The Thirty-Nine Steps. " For anybody else wondering what The Thirty-Nine Steps is: https://en.wikipedia.org/wiki/The_Thirty-Nine_Steps
> The first thing that one asks is that the adventure should be various and exciting; in this respect Mr. Tolkien’s invention is unflagging, and, on the primitive level of wanting to know what happens next, The Fellowship of the Ring is at least as good as The Thirty-Nine Steps
He's clearly suggesting that in one very particular respect, he values the 39 Steps so very highly that it can be used as a kind of measuring stick.
It may not seem like such a big deal, but partial quotations of this nature are the source of so much internet misunderstanding and drama these days.