What design layout do studies (if any) show is more effective when reccommending content to users based on their past user data?: horizontal lists similar to what we see on Amazon's product pages or having just one or two recommendations at a time within a right column as Facebook does? Both are effective in their own right but I'd like to know which vehicle enables users to make more concise decisions.
Knowing that users read in a "F" pattern. Source: http://www.nngroup.com/articles/f-shaped-pattern-reading-web-content/
And knowing that users spend 69% of their time viewing the left half of the page and 30% viewing the right half. Source: http://www.nngroup.com/articles/horizontal-attention-leans-left/
And also knowing that users spend 80% of their time looking at information above the page fold. Source: http://www.nngroup.com/articles/scrolling-and-attention/
The optimal positions for rec box would be:
Grid of cards is one option that I would recommend. Every recommended item would be on a card with a tittle footer note stating why this was recommended(say based on genre as of previous item) and this would be taking up the column 1 and on next column, it should be based on some other criteria say author in case of books and so on. So the final interface would like like a 4 X 4 grid of cards laid out.