I would recommend a teacher for anyone starting to play double bass. It's too easy to develop bad habits early on and having someone who can look at your posture and technique with an educated eye will save you a lot of discomfort. A good teacher will be able to recommend some books.
@Ned Smith, I'd estimate that at any age over around 40, an important question for you to consider is what kind of music you want to play double bass for. Life is short, and some genre and musical positions need 20 to 25 years of schooling and experience combined to achieve. Considering what kind of music you want to be involved with would help you target what kind of book, and even more, the kind of teacher you'll want to be using.
As someone who started working on double bass in my mid 60s, I've appreciated the importance of setting realistic goals of where I'll be taking my double bass playing.
All the good advise before and to follow, grab the Ray Brown book. He distills the Simandl concept and gives you the basic tools to all the primary jazz and pop scales and especially very efficient finger patterns. Good luck and keep us posted!