I am a newbie to Meraki products. Where could I found some books and videos on how to setup the MX100 and MX425? Please advise!
There's no books that I'm aware of. There are a bunch of videos, both from Meraki and not, on YouTube.
Honestly though, the documentation has most of what you'll ever need.
You can also do the CMNO certification which is a good beginners course.
Your best friend is going to be Meraki Documentation, Meraki Support (cases can be opened from the dashboard Help section, as well as phone numbers listed for your area), and here on the community.
You may be able to get some expert help from your purchasing partner, assuming they have experience and expertise with Meraki equipment.
You might be able to find a video or two on YouTube to show some basics, but I wouldn't bet on finding anything super specific. Most networks are going to be tuned to business need.
And, of course, if you have any specific questions on best practices etc be sure to ask them here. There are a lot of great people in this community that could help short-circuit your learning curve.
Good answers and guidance so far, I also wanted to point out that there's a whole Meraki YouTube channel that you can basically treat like a free training resource. https://www.youtube.com/user/milesmeraki/videos and you'll find general overview videos and past webinars, product overview webinars, and some more specific to a certain topic, like SDWAN for example. Leverage this Meraki Community, and get to know the Documentation site, and open a Meraki Support case if/when needed.
Also check out the Meraki Webinars site https://meraki.cisco.com/webinars and register for one and get a free piece of equipment (if eligible).
One other thing to remember is simply using the search feature built right into Dashboard. On any Dashboard page, simple type the forward slash '/' to pop open the search bar, and when you type a certain keyword, you'll typically see "Configuration" results and "Support" results. For example, go type / and then RADIUS. The configuration results will provide links to the actual page(s) in your own Dashboard network where you configure that feature. The support results will scrape the article from the documentation site and you can view the support docs without ever leaving your Dashboard environment. Just a couple little simple things that are sometimes a big deal!
In addition, get with your local Meraki Systems Engineer and ask them to arrange for a "Minilab" event in your area. A Minilab includes a Meraki overview but more importantly and more fun, multiple hands-on labs. All you need is a laptop and you'll have a full stack of remote live equipment to configure and test. It can be a great day of learning all-things Meraki, but the instructor can also perhaps modify the Minilab accordingly based on what the audience want to focus on more, like wireless, or security, or SDWAN, etc..
Hope that helps!