1.17 Pre-release 1 marks the point of feature-completeness for the update; from now on only bugs will be fixed in future pre-releases.
This pre-release readds the candle block as well as its crafting recipe. The candle was removed a couple of weeks ago due to incompleteness, and has been readded with a new lit texture.
Speaking of light changes, signs are now a lot more visible when glow ink is applied to them, having an outer glow now.
As is usual once an update reaches the pre-release period, a bunch of new achievements and menu splash text messages have been added, and the credits have been updated.
The achievements relate to the new features added in 1.17 and their names are always puns, as is common in video game achievements. These include "Whatever Floats Your Goat!" achieved when entering a boat with a goat and "Is it a Bird?" when looking at a parrot through the new spyglass.
New splash messages include Schwarzenegger reference "Get to the coppah!" and "[this splash text has been delayed until part 2]" which references the split of the Caves & Cliffs update into two separate versions.
Once the pre-release period comes, the full release of the update is nigh; expect 1.17 to release sometime in June.