The new system appears to follow the Google-type minimalist search field. I tried the search and entered part of the title of a book I was looking for. I entered, "Little Colorado River." The search results found the book in the number two position.
The blog post cited above, "A Better System for Searching Books—Troy Mohrman at RootsTech 2019," explains the following:
“What is LIMB Gallery?” Troy Mohrman, who works for LIMB Gallery, asked this question during his presentation “Digital Asset Management: There Is a Difference,” which he gave on Access and Preservation Day at RootsTech 2019.
Mohrman explained that LIMB Gallery is the new system FamilySearch uses to display books. LIMB Gallery was created by i2S Innovative Imaging Solutions, the same company that produces book scanners used by FamilySearch and others.
LIMB software can be used at each stage of scanning, processing, and publishing books online. “You are an institution that has spent a lot of time digitizing books; now how do you present them to your users?” he asked.The new system improves and updates the book searching capabilities of the FamilySearch.org Books project. Here is another quote from the blog post.
The new FamilySearch book system offers a complete text search. The system allows seeing text matches in context and moving easily from one text match to the next one.
As an example, Mohrman searched for the name Vonderfecht with the previous FamilySearch book interface. The old system found 5 results. Two weeks before RootsTech, the system changed to LIMB Gallery. Mohrman searched for the name Vonderfecht with the new system, and it returned 28 results, even though both systems were searching the same set of books.
To use the new system, go to Familysearch.org, select Search in the toolbar at the top of the page, and then select Books in the drop-down menu.