Proust likens his book to a sort of “optical instrument" that enables the reader to read herself.

 Yes! It is, I would say an optical test not instrument, a figure and ground test.

 If you see two faces, they are reading themselves. If you see a vase you are reading the background.

...a frequent experience while reading In Search of Lost Time is to look up half-way through a sentence and stare into the middle distance in a kind of mnemonic reverie or “epiphanic swoon”..., only to find, catching sight of a clock out of the corner of one’s eye, that whole hours have passed.

You see? Why would you want to miss the "epiphanic swoon" for the CLOCK! That is precisely the wrong way to read anything but especially Proust.

For it is the sheer length of In Search of Lost Time, compared to which War and Peace is but a diplomatic incident...that turns the phrase “reading Proust” from the designation of an ordinary activity into a cultural superlative, the literary equivalent of climbing Everest...

Now, there's a prize at the end 🥇, gold medal cultural superlative for reading Proust. No. There's no prize, no goal, no best time, just the flow of the Nile.