Since it opened, to considerable fanfare, a little over three years ago, it has generated so much public excitement that the number of daily users has doubled from when the collection was housed in its old building across Fulton Street.
There is, however, a snag. The library does not have anywhere near enough space for its primary purpose of storing books.
The architects who dreamt up New Main, as the building is known, may have done a fine job of creating a compelling space that blends in with the beaux-arts style of City Hall and the other public buildings on United Nations Plaza. But they were strangely uninterested in the books, apparently believing that the new digital age would soon make them surplus to requirement.
And that is a problem, since the city's voters approved the bulk of the building's $137m (pounds 91m) price tag on the understanding that it would house the existing collection and also have room for additional collections over the next decades.
A preliminary city report published this month said that the 32 miles of shelving are already full, as many as 200,000 books have been "discarded", that is to say, sold off, given away, or sent to landfills.
The report lambasts just about every aspect of the building. "People are baffled how to proceed once they enter the building," it notes, something to do, perhaps, with the fact that three of the four entrances leave you on a closed mezzanine, forcing you to take a very unobvious staircase down to a semi-basement before proceeding back up again.
"Critical library functions are poorly arranged and do not function well," the report continues. That refers to you having to return books in a different location from the check-out. It is also a rebuke of the automated restocking system, whose chutes and conveyor belts regularly batter and chew up books and leave them abandoned in the basement for up to a month.
The report has come as little surprise to library workers, or to long- standing critics such as the author Nicholson Baker.
Mr Baker took one look at the central atrium and reeled at the "large grey structure with a hole in the middle where the stacks should be". He wrote: "Space, from the point of view of a collection of books, means something quite different from floor space, atrium space, or even bandwidth in a telecommunications cable, all of which the New Main has in relative abundance. To a book, space means shelves."
Even the chief architect, James Inigo Freed, has described his creation as "a glittering void". Given the participation of telecommunications companies in the $22m chunk of private money that went into the library, many detractors suspect that the shelf space was deliberately short-changed so the library could eventually sell its services online for profit.
The hurried discarding of 200,000 books - just under 10 per cent of the total - caused an outcry when it was first brought to light, with one librarian describing it as a dirty secret that seeped out like blood from under a door.
The city may now be reluctant to shell out for new building space, leaving little option but to continue the cull - albeit more slowly and more carefully - in future.
"The cure could be as bad as the problem - killing books, destroying books or off-loading some functions in other areas,'' said Peter Warfield, who was part of a users' focus group involved in drafting the report.
A library that destroys books faster than it acquires them? That might be a popular policy in rural Alabama, but in San Francisco it is cause to weep.