Challenge 1: An Infinite List of Even Numbers — Possible Solution
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Main.hs:

evens :: [Integer]
evens = [0, 2 ..]   -- a generator-based infinite list, stepping by 2

main :: IO ()
main = print (take 8 evens)

Output:

    [0,2,4,6,8,10,12,14]

Explanation:
[0, 2 ..] is Haskell's arithmetic sequence syntax -- giving the first
two elements (0 and 2) tells the runtime the step size (2), and the
missing upper bound makes it genuinely infinite, exactly like
haskell1-1's own [1..] example. Nothing about writing this definition
computes any values at all; take 8 is what actually demands the first
eight elements, and only those eight are ever computed.

An equally valid self-referential alternative:

evens :: [Integer]
evens = 0 : map (+2) evens

This defines evens in terms of itself, the same style as the
chapter's own fibs example -- each element is the previous one plus 2,
computed lazily one at a time as take demands them.

WHY THIS WORKS AS AN ANSWER
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This defines a genuinely infinite list (both via arithmetic sequence
syntax and, as an alternative, via self-reference matching the
chapter's own fibs pattern) and safely inspects only a finite prefix
of it with take, exactly the safe-peek pattern the chapter's own
tip-box recommends.