The Berkshire Record Office (BRO) holds wills, or grants of administration for those who died without a will, from 1480 to 1857. These records can tell you a lot about someone and their relatives.
Until January 1858, the Church dealt with wills and probate, as soul and property were joined together. The BRO has records of two church courts that granted probate up to 1858: the Archdeacon of Berkshire, and the Peculiar of Faringdon. The Archdeacon oversaw wills of people with property in Berkshire, unless they owned land elsewhere or lived in one of the 'peculiars' - places where court jurisdiction had been granted to another Church official.
A complete index to the Archdeacon's collection, 1480-1857, is available at the BRO. The index to probates granted by the Faringdon Peculiar Court is available here.
For post 1858 wills see the GOV.UK website.