Errata (in my judgement) in Fractured Fractals and Broken Dreams (1997) by G David and S Semmes:
In formula (8.5), in definition 8.5, it is very possible that $x$ and $y$ belong to $F_j \cap B$ -- otherwise $B$ would not play any role!
In Definition 8.9, $K$ is replaced, inadvertently, with $L$, as the biLipschitz constant.
Two lined before Remark 8.14, the word "taken" is redundant.
Errata (in my judgement) in Differentiable Structures on Metric Measure Spaces: A Primer by B Kleiner and J.M Mackay (the published 2016 version):
It is not clear whether in the definition of charts, the case of N=0 is allowed. This is important since a priori, it is not ruled out that that on a set of positive measure we could have that every Lipschitz function is zero up to order one, so that an "empty" collection of coordinate functions suffices to write down any Lipschitz function up to order one. This must again be addresses in the proof of Proposition 4.1 (existence of differentiable structure). One practical way out is to cite a lemma from Cheeger's paper which claims that there do exist Lipschitz functions with nontrivial (=nonzero) derivative. But note that the latter depends on a Poincare assumption, which is not made yet when Proposition 4.1 is proved in Kleiner and MacKay's work.
In Definition 3.7, there is a double-use of $x$ as the fixed base point of the limit space AND then in the requirement for the convergence of functions "for all $x$''. Renaming the base point to $x_0$, or else choosing a different dummy variable name in "for all" would resolve this.
Errata in Absolutely Continuous Functions of Several Variables (1999) by J Maly:
On page 502, in the proof of Theorem 3.6 (coarea formula), in the second line of the big calculation part, the closing bracket "}" is missing, it must be placed at the end of everything: the sum is over the whole inside.
Theorem 4.1. One may wish to begin the proof by first choosing the continuous representative of the function. This step may have been assumed implicitly.
In proof of Theorem 4.3, in the middle term in formula (4.3), one must drop boundary (\partial) from the integral over $\partial B$, or alternatively, one must put $C_m$ up front in this term as well.