That's wonderful! Expressing gratitude and appreciation to a writer for their work can be a great way to encourage them and show your enthusiasm for their story. Here's a suggestion:
"Dear, Kara & Michelle,
I just finished reading your book, [Breeder Nation], and I wanted to reach out and express my heartfelt appreciation for the amazing story you've created! Your writing is captivating, and the characters and plot had me hooked from start to finish. Your talent and dedication shine through on every page.
Thank you for sharing your gift with the world! Your book has made a significant impact on me, and I'm so grateful to have had the opportunity to read it. Keep writing, and I look forward to your future works!
Sincerely,
Akshara. R.S