Is this for free or for a fee?
Are you sure it is genuine as Microsoft were offering a free upgrade to Windows 10 but this stopped a few months ago so I am surprised they are still offering it.
It may be a scam so be careful of putting personal info in a reply or clicking on any links.
To answer your question, Windows 8 was awful, a right mess, and Windows 10 is a better.
However as with any upgrade from one version of Windows to another it can go wrong and stop your PC working properly so you may need to get a person in to fix it for you.
Also the new Windows files are huge and they need to be downloaded from the internet so that can take a long time on a slow internet connection.
Overall I think you are better off on Windows 10 than Windows 8 (it is supported for longer for a start) but only you can decide if you want the hassle or the risk.
Make sure you back up ALL your personal files to an external hard dive before you do the upgrade.