There is a CCIE book list recommended by Cisco for the Routing and Switching exam(s). You do not need to buy all of them. The original book list is 21 books and contains many old books.
Below is a subset of the official list, updated and truncated for the best out of the list.
The books can be expensive, so keep an eye on the Amazon Market place and pick up a bargain if you can.
You can grab these books from all good Amazon stores:
The Essential CCIE Book List
1: CCIE Routing and Switching Certification Guide Volume 1
2: CCIE Routing and Switching Certification Guide Volume 2
3: Cisco CCIE Routing and Switching v5.0 Configuration and Troubleshooting Practice Labs Bundle
4: Routing TCP/IP, Volume 1
5: Routing TCP/IP, Volume 2 (version 2)
6: Troubleshooting IP Routing Protocols (CCIE Professional Development Series
7: Cisco LAN Switching (CCIE Professional Development series
8: Developing IP Multicast Networks, Volume I: 1
9: Internet Routing Architectures (2nd Edition)
10: MPLS and VPN Architectures (Vol 1)
11: MPLS and VPN Architectures: v.2: Vol 2
12: Cisco Catalyst QoS: Quality of Service in Campus Networks
13: End-to-End QoS Network Design: Quality of Service in LANs, WANs, and VPNs
14: Deploying IPv6 Networks
15: Network Security Technologies and Solutions (CCIE Professional Development
Buying the entire CCIE book list will be expensive, so getting these on a Kindle might be a worthwhile option. Some of the books are £10 or so cheaper on the kindle than on paperback, and the added advantage is that they can be taken anywhere easily.
Kindles are fairly inexpensive and can be picked up for just over £100 for a Paperwhite, or around £150 for a Kindle Fire.
New SDN & IoT section
The list above does not include new topics, but check out the books that will be useful for the Evolving Technologies section of the written exam.