In reply to Exile:
two other guidebooks that might be useful:
https://www.libreriadesnivel.com/libros/escalada-en-roca-en-los-picos-de-eu...
https://www.desnivel.com/cultura/cultura-libros/cabrales-la-esencia-de-la-e...
There are quite a bit arround picos de Europa as well which you will find some in Cordillera Cantabrica guidebook. You can buy this in the many villages around Picos. I think it is impossible to find it online.
If it is the first time you go there just do the most recommended ones as they are great. A few highlights:
- Murciana in Naranjo del Bulnes (west face): a bit a aid climbing for the crux pitch but the rest goes around 6a/+
- Amistad del diablo in Naranjo del Bulnes (East face) (V+)
- El rojo libanes in Horcados Rojos (6b+)
A small note, summer can be very hot, even in northern Spain. Outside of Picos range you will be a bit too low in altitude (for my taste at least) to be able to have fun climbing in the sun. Even up high can be a bit too hot! An example: the main route in Cueto Aguero just outside of La Hermida gorge is great but not to be done in a hot clear day in summer!
A recommendation, in case you are into this kind of things. A great thing to do in Picos is to mix between trekking and climbing. Pack your rucksack for 5-6 days walk to some hut (sleep there or in a tent), climb a route there in move the next day and climbing in another area. You get to know Picos quite well and each corner has its delights.