I am making some bookshelves, and have 1" red oak planks in varying
widths from 6" on up to about 11". To make my shelves at 11 1/16"
thick, I have been ripping my planks down to a maximum width of about
3.5", and joining 4 pieces together.

I had heard that to avoid splitting or cracking of wood, it was best
to rip down to this width and then join back up.

My question is whether this is good advice. Do I really need to rip
all my wood down like this, or can I join two 6" pieces if I want to?

Scott