Is Gesenius' Hebrew Grammar a searchable electronic text or is it a pdf or something?
All Logos resources are searchable, linked electronic texts.
When you click on sample pages in the bundle it just looks like a pdf...
The sample pages are always scans, usually added before the book is produced. On the individual product page, click See Inside to get a better idea of what the product looks like in Logos. However, I've noticed that that feature is barely working now, and you can only see a few pages. You used to be able to see much more. I've reported that as a problem, and hopefully it can be fixed fairly soon.
Most of the samples I've seen are not fully representative of the final product.
Here's a screenshot. It looks like any other regular resource - linked and searchable:
