Problem regarding Errors after Theoremdefinition using thmtools

Question

I am currently hunting for errors in my template and these two I cannot solve after reading the log and researching:

First:

! Argument of \strip@prefix has an extra }.
<inserted text> 
                \par 
l.60                postheadspace=\newline]{mystyle}

Second:

! Paragraph ended before \strip@prefix was complete.
<to be read again> 
                   \par 
l.60                postheadspace=\newline]{mystyle}

Minimal example:

\documentclass[a4paper, 12pt, oneside]{book}

        \usepackage{amsthm}
        \usepackage[unq]{unique}
        \usepackage{thmtools}
        \declaretheoremstyle[
                numbered=unless unique,
                %within=chapter,
                headpunct={},
                shaded,
                spacebelow=\parsep,
                spaceabove=\parsep,
                notefont=\normalfont\itshape,
                bodyfont=\itshape,
                postheadspace=\newline]{mystyle}
        \declaretheorem[
                style=mystyle,
                name=Theorem,
                refname={theorem,theorems},
                Refname={Theorem,Theorems}
        ]{FF}

        \usepackage{hyperref}

        \usepackage{cleveref} 
        \crefname{FF}{Theorem}{Theorems}
        \Crefname{FF}{Theorem}{Theorems}

\begin{document}

\begin{FF}\label{ff1}
Test
\end{FF}

Link to \Cref{ff1}.

\begin{FF}\label{ff2}
Test2
\end{FF}

\end{document}

Answer 1

The shaded key requires a key-value list (see page 15 of the thmtools documentation); also, the unless unique option seems to require the unique package:

\documentclass[a4paper, 12pt, oneside]{book}

\usepackage{amsthm}
\usepackage[unq]{unique}
\usepackage{thmtools}
\usepackage[unq]{unique}
\usepackage{xcolor}

\declaretheoremstyle[
                numbered=unless unique,
                within=chapter,
                headpunct={},
                shaded={bgcolor=blue!20},
                spacebelow=\parsep,
                spaceabove=\parsep,
                notefont=\normalfont\itshape,
                bodyfont=\itshape,
                postheadspace=\newline
]{mystyle}
\declaretheorem[
                style=mystyle,
                name=Theorem,
                refname={theorem,theorems},
                Refname={Theorem,Theorems}
]{FF}

\usepackage{hyperref}

\usepackage{cleveref} 
\crefname{FF}{Theorem}{Theorems}
\Crefname{FF}{Theorem}{Theorems}

\begin{document}

\begin{FF}\label{ff1}
Test
\end{FF}

Link to \Cref{ff1}.

\begin{FF}\label{ff2}
Test2
\end{FF}

\end{document}