Nearly 350 libraries have closed in Britain over the past six years, causing the loss of almost 8,000 jobs, according to new analysis.
In a controversial move that sparked protests by authors including Philip Pullman and Zadie Smith, councils across the country have shut their reading rooms in an effort to make deep savings.
Children's author Alan Gibbons warned the public library service faced the "greatest crisis in its history".
The figures, obtained by the BBC English Regions data journalism team, showed that 343 libraries have shut since 2010 and another 111 closures are planned this year.
A further 174 libraries have been transferred to community groups and run by an army of volunteers, while 50 have been handed to external organisations.
Gibbons, who wrote Shadow Of The Minotaur, told the BBC: "Opening hours are slashed, book stocks reduced.
"Volunteers are no longer people who supplement full time staff but their replacements. This constitutes the hollowing out of the service. We are in dangerous territory."
Librarian Ian Anstice, who runs the Public Libraries News website, said the cuts were "without precedent".
He said: "Councils learnt early on how unpopular simply closing libraries is, so they have had to cut the vital service in other, less obvious ways.
"It can come across in many forms - reduced opening hours, reduced book fund, reduced maintenance and reduced staffing.
"In all its incarnations, it is harmful to the service, creating the risk that once-loyal users of libraries will come away disappointed and stop using them.
"Our public library system used to be envy of the world. Now it is used as a cautionary tale that librarians use worldwide to scare their colleagues."
Four areas - Sefton in Merseyside, Brent in north-west London, Stoke-on-Trent and Sunderland - have seen over half their libraries closed since 2010, the BBC data team said.
A spokesman for the Department for Media, Culture and Sport said: "Libraries are cornerstones of their communities and are part of the fabric of our society, so it's vital they continue to innovate in order to meet the changing demands of those they serve.
"Government is helping libraries to modernise by funding a wifi roll-out across England that has benefited more than 1,000 libraries and increasing access to digital services and e-lending."