First up: A Mathematician's Apology (1940) by G. H. Hardy, a work on which Graham Greene remarked "I know no writing—except perhaps Henry James's introductory essays—which conveys so clearly and with such an absence of fuss the excitement of the creative artist." (The Spectator, December 20, 1940).
The first line in the book is:
It is a melancholy experience for a professional mathematician to find himself writing about mathematics.The first line in C. P. Snow's 1967 biographical foreword to AMA reads:
It was a perfectly ordinary night at Christ's high table, except that Hardy was dining as a guest.