The county council is starting a radical restructuring of its services, meaning a loss of 27 posts and pay cuts of about £4,500 for a further 17 staff.
Unison members voted earlier this month for industrial action after the long-running dispute with library heads over the future of the services.
Some libraries, including Fareham and Gosport, are likely to be closed by the strikes, as well as some smaller branch libraries.
The strikes will not affect Portsmouth - which is controlled by the city council.
Hampshire says it wants to make changes to its current employment structure so it can keep libraries open and increase opening hours.
However, librarians say the changes will lead to a 'de-professionalisation' of the service.
Hampshire Unison rep Steve Squibbs said: 'What management are proposing will not just affect library staff but will also have a drastic impact on the standard of service that Hampshire residents receive.'
The libraries in our area confirmed to be closing because of strike action on Thursday and Friday are Fareham, Gosport, Hayling Island (already closed on Thursdays), Lee-on-the-Solent.
However, others may also be affected.