"Big Finish was looking for a way to do stories with the First, Second, Third and Fourth Doctors, and Nick [Briggs] came up with the inspired idea of telling stories from the perspective of the companions," explains the current range producer, David Richardson.
I was a little disappointed with this big heavy glossy book; it simply lists the Big Finish plays up to about 2010, with cast list, plot summary, and a few almost invariably positive words of description from those who were involved with the production. This is fine for enjoying the triumphs (where indeed I, Davros is a clear winner among several high points) but it means that the nadirs (eg Nekromanteia, The Poison Seas) are rather glossed over. The book also has similar surveys of several of the Big Finish ranges which I simply don't know at all - Sapphire and Steel, Highlander - and might now try. But for what it is, it's rather overpriced.
It was sad to read that the Sapphire and Steel range was basically discontinued because of too much torrenting. I wonder if that would still be the case today.