This is a new resource, not from us but from the Borders Family history society. I wanted to mention it though as it dovetails with what we do so I thought you may be interested. You can read all about it on their blog.
Remember they give a list of surnames in each volume, which is very helpful. If you are considering buying a few books it’s worth joining the society as Society members get a discount of £1 per volume not to mention all the other benefits of joining the society.