In our quest to give everything Anglocentric common names it's surprisingly easy to forget that the world of insects doesn't evolve around Britain, not by a long stretch. A large proportion of the latest entomology-related research is carried out in institutes across Scandinavia, and field guides like these two are a testament to this.
Fjadermott i Norden is a pocket-sized Swedish guide that illustrates all 58 species of plume moth found in Scandinavia, many of which are also present in the UK. I won't claim to be able to understand a word of it, but the book's in-depth coverage of larval stages combined with fantastic illustrations was reason enough to part with a tenner for it.
The other book I purchased is called Suomen Luteet - translated simply as 'Finnish Bugs'. It was an impulse buy having been recommended to me 10 minutes earlier by good pal and leading hemipteran guru Tristan Bantock. The layout is simple and an impressive array of species are described (a hefty proportion of which are also present in the UK) using high quality photographs of mounted specimens.
As far as I'm aware, there are no other books available that cover Hemiptera in such a comprehensive manner, and at £35 it's a bit of a bargain. The only pricey bit will be the subsequent Finnish language classes you'll need to be able to read it.