This is true in a perfect market, based on Modigliani-Miller theory of capital structure.
In reality, increasing debt to a certain point also increases risk, which in turn increases return on equity.
In reality, increasing debt to a certain point also increases risk, which in turn increases return on equity.
When a company takes a loan, even if that loan is so large as to make insolvency almost inevitable, there is no impact on equity (book value).