Like most people my age, I grew up with the Wizard of Oz movie, but hadn't read the book. It didn't occur to me to until I met my father-in-law, who is somewhat obsessed with Oz. He grew up the book, but not our book. No, he grew up with the Russian Oz, written by Alexander Volkov, which features a young girl by the name of Ellie travelling to Magic Land with her talking dead. Imagine his surprise when he came to Canada and discovered a whole alternate universe of Oz, by a different author, and even a Hollywood movie! 
 He showed the movie to my son, and his enthusiasm must have been contagious (perhaps aided by the Wicked Witch popping up in LEGO Dimensions), because my son loved it. 
 The time seemed as ripe as it would ever be to finally read Baum's Wizard of Oz at bedtime. 
 It holds up beautifully. The language is only very slightly Old Timey, but was modern enough to be perfectly comprehensible for a modern, 21st century kid (peppered with a few bigger words to help with a child's expanding vocabulary). He enjoyed revisiting the characters, seeing their additional adventures, and even noticing the differences between the movie and the book (in particular with the pictures, drawn by David McKee, which are wholly independent from the Judy Garland movie's imagery). 
 For my own part, I enjoyed it. It was very whimsical, with solutions often popping out of thin air just as they are needed. It's an episodic book, with creatures being introduced, dealt with, and then disappearing forever - so the book lacks much of a narrative build. That makes it quite perfect for bedtime reading, as sleepy kids aren't great at keeping track of plot threads. 
 I don't know how well the book would be received if it were written today, just because we tend to be a bit more narratively demanding - even with out children's books - but it was fun. It throws a lot of ideas around, but doesn't overplay them or resolve things too neatly, so there's a lot of room for imagination. 
 In conclusion, we enjoyed it. It held my five year old's interest, as well as mine, and it gave us a good way to finish up our day and prepare for bed.