Welcome to Basschat, Ashweb! When I started playing bass in my early 40s I had never played an instrument before. Don't let that deter you.
I also used the Dummies book, but to start with I would recommend a few one-to-one lessons, or at least a short course in a small group of students, with a good teacher. Believe me, it makes progress as a beginner much easier, and cures you of any bad habits you may not have realised you are acquiring. Take a look around the forum, find a Basschatter who teaches near you, and have a word with them.
And join us in our discussions. Feel free to post any queries you may have - we have a lot of very helpful experts who will be happy to give you answers.