I plan on flying to Austin, TX in January, 2019. Will I need a passport? If so will a card do or should I get the book? I do not do a lot of traveling?

Are you thinking of Real ID driver's license requirements, rather than a passport? You'll need to check with individual state requirements; many have enacted extensions, so you might not have to rely on additional forms of identification (like a passport) when traveling.

Passcard works for all States and US territories

I'm assuming you live in Maine which is apart of the United States and so is Austin, TX. All you'll need is your ID