Make your ebook social media friendly, promote your social media accounts, ask your readers to spread the word, tweet about it, use hashtags, start and monitor conversations about it, make a page for your book on Facebook, offer your book as a prize - it will get people interested and talking about your book. Use niche networks such as LinkedIn. There you can add a publications section to your profile, then add your book to this section, create a readers' discussion group for your book, name your book as part of your LinkedIn summary, so anyone checking out your profile can see you're an expert in your field and post quotes from your book in your LinkedIn updates.
Firstly I would suggest creating a Facebook group that is dedicated for that ebook. Later on you will need some reesources so as to implement Facebook advertising campaign. I would suggest beginning with page likes - your advertisement will show up for the people with the preferences you have chosen while setting up the campaign (your target audience). So begin with the likes so as to increase the visibility of your book and later on you can try other Facebook campaigns.