Libraries in Wales should be coordinated nationally in the future, a panel of experts has recommended.
The report, for the Welsh government, came as councils consider closing libraries because of budget cuts.
The Expert Review of Public Libraries in Wales calls for initial three to five year plans to run library services at a regional or national level.
Ministers said financial strains on public services meant the current model was "unlikely to survive".
The review concludes there will be "far-reaching changes and a reduction in public library service provision" and calls for more collaboration between libraries, council departments and local authorities themselves.
The Welsh government commissioned the study last year to find "sustainable future plans".
Deputy culture minister Ken Skates said the report would be the basis of discussions on the future of libraries.
Ceredigion council leader Ellen ap Gwynn warned last week that financial pressures meant the council could "cease to provide buildings" for libraries in the future and offer a fully mobile library service, which could also offer other council services.