Here are a few specific online booksellers you can learn best practices from through researching their platforms:

- Amazon - As the industry leader, Amazon has refined their processes extremely well. Study how they optimize book profiles, categories, customer reviews, related item suggestions, and other data-based personalization.

- Barnes & Noble - While their retail stores face challenges, their well-organized online bookstore is still a top channel. Learn from the design of their categories and book pages for optimal browsing and discovery.

- Book Depository - Owned by Amazon but known for excellent international reach and low/free shipping worldwide. Analyze targeting strategies for global audiences.

- ThriftBooks - A prominent used/remainder bookseller with great techniques for sourcing inventory cost-effectively while sustaining quality control standards.

- Alibris - With vast selection of rare/out-of-print titles, they showcase innovative ways of keeping niche works discoverable to readers despite lower sales volumes.

- College Bookstores - Platforms like Barnes & Noble College/Follett showcase merchandising tactics for serving student communities with curated course material mixes.

- Independent Booksellers - Websites of indie stores scattered worldwide exemplify personalized bookstore feel for online. Mining reader reviews/events works.

Paying close attention to top performers like these allows self-publishers to replicate engagement drivers and continually raise the bar on customer experience across all channels. Let me know if any specific area could use more analysis!