I'll second that...
I played D&D a lot as a kid (Basic Set and later AD&D)... then took a long break and I played a little tiny bit of 3.5, and later some 4e.
I finally got a chance to DM some 5e - so we started with Lost Mines -- which I highly recommend for new players & DMs. It was pretty well done although I think the module should have gone into a lot more detail about DM options at each point and been a little more clear on the story-line. I tend to get the rules mixed up with older versions - like spell casting would invoke opportunity attacks... whatever. They lived

So next up I picked Out of the Abyss... Vastly more complex -- this is really more of a campaign setting than a well-laid out module so you have to build the adventures yourself. They give you lots of random tables to roll on which is ok for some variety but I threw that out almost immediately and I used the random tables to help inform building out adventures along the way but I recrafted them in my own style and fit them to the players so they made a little more sense.
I LOVE OotA as a campaign setting but it's a LOT of work on the DM to turn the book into an adventure.
Be Prepared!