CCDA or CCNP

Just passed my CCNA exam, and I was just wondering if it is better to take the CCDA first or just start studyin for the CCNP then get CCDP? thnx

also, is it ok just to use the CCDA Exam Certification Guide w/o reading the CCDA self-study? when i studied for the CCNA i only used wendell odom's books

thnx...