For fiction books, I've heard of indie authors organizing groups where they read each other's books and write reviews. Some groups are more serious in that they actually analyze and suggest improvements to each others' work, but other groups work more as a "let's trade 5 star reviews" thing.
orionblastar
Please select a time for your Kindle book to be free to download and post it in r/freebooks and r/freekindle subreddits and ask for a review in exchange for giving your book away free. You can't always control the reviews to be positive though, and Amazon discourages bots from rating books.
mkbkn
Yes, reviews are very much needed for more sales.
How to get them - Post in free ebooks communities when the price is $0. Use Amazon Ads to promote the ebook.
Another way is to create a landing page and send traffic to it via ads.