This is indeed by itself a sufficient reason for writing a book ; but add to this what has many a time wrung books from modest authors, the impetuous appeals from known and unknown friends. Moreover, he had bought a big work, and, what is worse, had read it, and this labour was not to be thrown away. Thence originated the present treatise, which, we flatter ourselves, will fully satisfy the reader ; for the main part he will not understand, another part he will not believe, and the rest he will laugh at.
Kant, Dreams of a Spirit-Seer (download here)
"So soon as Swedenborg's Arcana Coelestia was printed, for whose publication he had been eagerly waiting, he bought the volumes at seven pounds sterling, and this at a time when Kant, the privat-docent, was anything but well off, and when that amount of money meant more than it does now."
Thanks to Alberto for noting Kant's recognition of the need for a review copy...