Almost leisurely until the not-intensity-but-something-like-it slams into you. Like a mirror rushing towards you but it's a mirror so you don't really see it coming and it hits you and shatters and you're left stunned, looking through broken reflections to the beyond, wondering where to go from here.

The kind of book you need take a long walk after reading, or perhaps a good cry (though you're not really sure why).

Science fiction like only Becky Chambers does it.