Many of the Camino routes are well way-marked so you could manage without any maps or books but a guidebook would helpful, in particular for locating accommodation and appreciating historical and cultural aspects of the pilgrimage.  There are a variety of guidebooks and maps available and we stock the most popular ones in our online shop.

There are also several websites that break down the routes into stages and provide information about the route (such as elevation maps) and accommodation.  Examples of these are

http://www.mundicamino.com/los-caminos/

http://www.gronze.com/

http://caminodesantiago.consumer.es/

Please see the Pilgrim Forum run by Ivar Rekve for various threads on GPS.

There are lots of apps available.  These can be found at the Apple and Android app stores, or at websites like these:

https://play.google.com/store/apps/details?id=com.alertcops4.app&hl=en_US -  Alertcops: free safety app

https://itunes.apple.com/es/app/app-camino/id1351903033?mt=8 - App Camino: free and comprehensive app for the Camino Francés

http://www.caminoapp.com/ - Wise Pilgrim

caminoways.com - free app

http://www.caminocommunityguide.com/camino-smartphone-app.html

http://www.keithfoskett.com/walking-el-camino-year-camino-companion-smartphone-app/  - free app

https://caminopilgrimapp.blogspot.co.uk/

This list is simply to indicate a selection of what is available. We haven't used or reviewed any of these apps so can't recommend any one in particular.