Project Hail Mary · Andy Weir, 2021
How far is Erid from Earth in Project Hail Mary?
16.3light-years
Erid circles 40 Eridani, 16.3 light-years from the Sun and about 10 from Tau Ceti.
From the book
Erid is Rocky's home: a heavy, hot planet, about 2 g, under 29 atmospheres of ammonia. It is so dark there that Eridians never evolved eyes. Rocky's side of the tunnel runs at 210 °C.
Its star, 40 Eridani, is an orange dwarf, and it is dimming too, which is why Rocky came to Tau Ceti. On the map Erid's orbit follows the real (and disputed) planet 40 Eridani b.
This is where the book ends, so there are spoilers in the scene behind the button.
See Erid on the star chart