A few years ago, many of the old volumes were scanned and put online for free, in word-searchable format.
Now, thanks to generous grants from The Mercers' Company and The Marc Fitch Fund, the balance (except for the last few volumes) have also been launched.
At the same time, two larger and more general volumes have been published;
The Stirling Region (edited by Timms) (1976) and
Central Scotland, Land, Wildlife, People (edited Corbett and Dix)
You can now download all this material from the FNH website