When I had adjusted a photo in Aperture a second version was established with the changes. Those files imported into Lightroom with two versions, but the second does not seem to have carried with it the adjustment changes made in Aperture. Does that mean I should delete the second copy in Lightroom?
Not sure what you mean. Aperture starts with a master file. When you make adjustments, the adjustments are made to the singular "version" of that master file, and the adjustments are stored as metadata, and as a thumbnail. If you create a preview for that photo (automatically or manually), or export the photo, a higher resolution version of that master image, with adjustments, is created.
You can create more than one version, and are typically shown in a stack in Aperture. For example, I might edit a photo. Once done, I may create a second version and turn it black and white. Then I might create another version for a 4x3 aspect ratio, and another with a 5x7 ratio. Thumbnails are create for each, and previews if desired.
When migrating to Aperture, it will migrate your master. I'm guessing this is one file in the set you see. Secondly, IF you created a preview in Aperture for this image AND you chose to migrate previews, THEN you should see both the master (unedited) and preview (edited result). Personally, I would not delete either. Or it could be, you have created several versions. You'll likely see only one master, and may see the previews. But I would be VERY careful that you're not deleting the master file. If it's a raw file (CR2/NEF), then you should NOT delete it. If it's a JPEG, you'll need to assess whether this is a JPEG master, or an unedited preview. But again, I doubt you'll want to delete either.
NOTE: In my tests, only 1/3 of the Aperture previews get copied over anyway. A bug in the plugin? Probably, but Adobe won't respond online or through support channels.
I do not think Lightroom can read and bring over adjustments made in Aperture. Is that correct?
Correct. Although you could use smart albums in Aperture to find and help keyword photos so you know what was done to them in Aperture. Would need to do this before your migration.