Logos has a copy of GKC, but it's very difficult to use because almost 100 pages (containing the Scripture Index) are not included on the Logos version. This book is public domain.
Would it be difficult to get pages 532-616?
The best way to use GKC is searching by verse, but there's no accurate way to do this with Logos. I always have to use a hard copy whenever I need to look up a verse.