There are different sets, but the oldest records who first purchased a particular tract of land. All the original land purchasers in Twp. 4 Range 12E will be listed together as will all the purchases in Twp. 4N Range 11E and so on. What is useful about this is that you know what property owners had land in the same neighborhood and I suspect when county property maps were drawn, they were developed from these books, not from the deeds.
Deeds are obviously the most widely available records.
You should check at the Indiana State Library for availability as they also have microfilms of many county records. Deeds are available for Jefferson County from its formation in 1811. Switzerland County was carved from Jefferson in 1814. Earlier county records essentially don t exist. Jefferson was created from Clark County, but few if any of the Clark deeds pertain to this area.