Indeed...Happy Birthday to Bilbo and Frodo!!
I think that the thing that struck me the most about this chapter as I started to read The Lord of the Rings
for the first time, was the decided change of tone
from the beginning of the chapter discussing the mundane everyday life of the Shire and the rather silly Hobbits (especially the Sackville-Bagginses and their jealousy of Bilbo and Frodo)...to Gandalf's stern confrontation with Bilbo as he eventually lefy the Ring behind and the hint of suspicion that Gandalf starts to reveal about the Ring.
Upon the first reading (and having little if any knowledge of the importance of magic rings in Norse mythology), I think I was initially as dumb as a post hardly suspecting that this Ring was going to be so powerful and dreadful....and...truly the plot of the whole story.
All I know is that I have always felt that the very last paragraph in the chapter is one of those keys to Tolkien's literary (story telling) prowess in that he leaves you in this idyllic setting of the Shire, yet also leaves you feeling anxious and unsettled because you just know something else is coming...
Frodo saw him to the door. He gave a final wave of his hand, and walked off at a surprising pace; but Frodo thought the old wizard looked unusually bent, almost as if he was carrying a great weight. The evening was closing in, and his cloaked figure quickly vanished into the twilight. Frodo did not see him again for a long time.
After the merriment and silliness surrounding the birthday party...what a masterful way to let you know that the times they are a changin'.