The books were created in partnership with the National Trust, so are heavily animal and wildlife based. You'll find quiet fishponds, families of badgers, herds of deer, cheeky otters, sneaky mice, a kaleidoscope of butterfly species and lots more. Here's a snapshot of how the format of the book is made up.
What I would say is that there is an awful lot of work required to colour a card an envelope as they are so crammed with detail, some of it quite small. You're not forced to colour it all of course, particularly the insides of the envelopes as they are very busy!
There are two more books planned in this series, Summertime and Christmas, releasing in June and October respectively. I cannot wait for the Christmas ones as I know they'll make lovely personalised cards for the festive season!
Here's a card I'm working on at the moment with my Marco Raffines.