Prerequisites

Schopenhauer sets forth the requirements for understanding The World as Will and Representation  in the preface to the first edition:

1. Read the book twice.
2. First read On the Fourfold Root of the Principle of Sufficient Reason: A Philosophical Essay.
3. Be acquainted with the principal works of Kant.
4. For preference, be acquainted with Indian thought.

Well,

1. That will take a while: the two volumes comprise about 1100 pages, and I have only started the second.
2. I didn't, but perhaps will take up the book this fall.
3. I thought that I was acquainted with Kant's work. However, the appendix to the first volume, "Criticism of the Kantian Philosophy", disabused me.
4. I am a bit weak on this point.

It would be fascinating to see the copies of Kant's works that Schopenhauer used, I imagine: what annotations must he have made? I can see that after setting Schopenhauer aside I should probably go back and read through The Critique of Pure Reason again.

The second-last paragraph of the preface runs

I am afraid, however, that even so I shall not be let off. The reader who has got as far as the preface and is put off by that, has paid money for the book,and wants to know how he is to be compensated. My last refuge now is to remind him that he knows of various ways of using a book without precisely reading it. It can, like many another, fill a gap i nhis library, where, neatly bound, it is sure to look well. Or he can lay it on the dressing-table or tea-table of his learned lady friend. Or finally he can review it; this  is assuredly the best course of all, and the one I specially advise.

In the Austrian movie "Das weite Land", based on Arthur Schnitzler's play of the same name and released in the US as "The Undiscovered Country", the doomed admirer of the industrialist's wife gives her a copy of The World as Will and Representation shortly before he shoots himself. I find that this cannot have occurred in the play, for when it commences the admirer is already dead and buried; whether the book turns up as a prop, I can't say, lacking the patience to find my way through many pages of Fraktur.