It's my experience that a lot of indie authors like to pick just any old day to release their new book. Often times, it's the day they finished uploading their ebook file to Smashwords or Amazon KDP. There is a science to book releases, however, and whether your book release is noticed or lost in the hordes of other books being released depends on which day you choose to release your book. So, I'm going to rank the worst days and then let you know what is the best day to pick.
#1 Worst Day: A National Holiday
I don't care what day of the week it falls on, NEVER release on a national holiday. Why? If anyone is marking that day on their calendar, they are marking it with what they are doing with friends and family, not your book release. Few people are at their computers (where they might purchase the book online) until very late in the evening, and even fewer are buying books. So, for anyone who has planned to launch their book on July 4th, turn back now and pick a different day.
#2 Worst Day: The Weekend, Especially in Summer
For the same reasons as above, the weekend (this includes Friday) is not a good time to try to attract eyes to your book release. Especially in the warm weather months, people have plans that don't include buying your book. Sometimes you'll get someone purchasing your book to take to the beach, but those sales are few and far between on a Friday, Saturday, or Sunday.
#3 Worst Day: Mondays and Wednesdays
Most people hate Mondays and "hump day", and for whatever reason, they hate being on the internet on Wednesday, too. Ever notice there is a marked slump in the number of social media posts you see in your feed? It's not because everyone is thinking of something to say, it's because no one is there. If no one is there, they're not seeing your book release announcement. On Monday, everyone is trying to recover from the weekend, not looking for a new read.
So, What's Left?
Well, the best day and the second best day, of course. Drumroll please.
The Best Day to Launch a New Book: Tuesdays!
Every new mainstream media release - DVDs, CDs, books - happens on a Tuesday. Think that's pure coincidence? Nope. That's called years of market research done by the mainstream producers and publishers, so follow their lead and release on a Tuesday.
But, won't my book get lost in the shuffle? No, because readers know to look for your book on a Tuesday, because that's when new books are released by the Big 5. They don't expect you to be any different, so you're not going to capture their attention better by being different.
If you can't for some reason - your book file got screwed up or your internet went out - the runner up is Thursday. You'll still get traction with buyers if you choose the next best day.