z/OS 2.1 Migration Guide and other resources

I mentioned an article by Marna Walle in Hot Topics where she also discusses the z/OS 2.1 Migration Guide and how they changed the format. But let me just quote her text about it :

'I can’t fit all of the information about migration actions into this one article, so make sure to review z/OS V2R1 Migration, GA32-0889.
Speaking of the z/OS V2R1 Migration book, you’ll notice that we’ve changed the format. We wanted to provide a more customized migration path to users, so we’ve divided the chapters in the book for those on a specific migration path. Chapter 1 contains an introduction to migration for all to use. Chapter 2 contains the migration actions just for those on the z/OS V1R13 to z/OS V2R1 path. Chapter 3 contains the migration actions just for those on the z/OS V1R2 to z/OS V2R1 path, which also includes all of the z/OS V1R13 migration actions. If you are coming from z/OS V1R13, you need only read Chapters 1 and 2 and Chapter 3.
If you are coming from z/OS V1R12, you need only read Chapters 1 and 2 and Chapter 4. We hope that you find this format easier to use and that it gives you a more useful scope when seeing your migration actions! Let us know your impressions'.

You can find the migration guide over here.

The title says : 'and other resources', so just know that there's an entire page dedicated to z/OS 2.1 migration and installation. You'll find a link to the Datasheet and the z/OS V2R1 FAQ in general.
There's a section with installation planning and migration resources where next to the migration guide you also find the z/OS Introduction and Release Guide, z/OS V2R1 Planning for Installation and some other useful publications.

Also, do take a look at the right side of the page under the 'Browse z/OS' tab : when you click on the Features and functions, Tools, Library and Support links, you get a nice pop up that refers you to more detailed information.