Most book marketing today is digital, involving online ads, newsletters, social media, and websites. Whether you're traditionally published or going the indie route, you're going to have to take on almost all of the marketing tasks on your book catalog, and the digital route may not be enough. The more ways you can get the word out when self publishing, the more people will buy your book. You sit at the keyboard all day while you write; why not use some retro techniques and practice guerilla marketing to spread the word.
Some printing companies online offer free business cards as a loss leader. Make up a pack of these cards using your book cover as the graphic and publishing info instead of address and phone number, and hand stacks of them out to friends and family. Ask everyone to leave them on tables in coffee shops, slip them into books at bookstores, drop them on library tables or doctor's waiting rooms, and anyplace else people gather and wait.
Local Book Clubs
Book clubs are still huge, and it's likely there's one in your community that's dedicated to your book's niche or genre. Contact the leader of the book club and offer to hand out copies of the books along with question guides. Let her know you're willing to speak with the club and bring the wine or a plate of cookies. When readers are enthusiastic about an author, they'll talk about him, and getting to know them personally is a great way to connect.
Make up stickers picturing your book cover with the address online where they can find it. Use these stickers in creative spots to get your name in front of people's faces. Paste them on water bottles and hand them out all summer at public events. Drop them in Halloween trick-or-treat bags. Talk your local coffee shop owner into sticking them onto a stack of coffee cups. Look through your neighborhood and find unique (and legal) places to sticker your environment.
The Book That Went 'Round the World
This marketing idea is half low-tech and half high-tech, but it's all creative guerilla marketing with a price tag of zero. Print out a copy of your book and sign it, adding a note on the flyleaf asking readers to sign the book, post a photo of themselves with the book on Facebook or Instagram, then hand it off to someone else after they read it. Bonus points if they give it away to someone in another state or country, maybe on vacation. Send four or five of these books around to see where they end up. It's a great way to grow your Facebook likes organically, as well as your mailing list and fan base. Make up a quickie website to post all the photos you find of your traveling book and its temporary owners and link it to your book sales page.
Keep The Faith and May the Force Be with You