Opening VLeBooks PDA titles

When viewing an eBook on the VLeBooks platform sometimes you will see the following screen, where the most obvious button says "Preview":

If you select "Preview" you will be able to access the full eBook. After 5 minutes a pop-up will appear asking if you want to continue accessing this resource. If you say yes, you will have to fill in your c-number, but then the title becomes permanent, and the next time you access it there will be the option to "Read Online" or "Download" instead of "Preview".