io.restassured.path.json.exception.JsonPathException: Failed to parse the JSON document

Question

[RemoteTestNG] detected TestNG version 7.8.0
FAILED: files.Dynamic.addBook
io.restassured.path.json.exception.JsonPathException: Failed to parse the JSON document
    at io.restassured.path.json.JsonPath$ExceptionCatcher.invoke(JsonPath.java:1002)
    at io.restassured.path.json.JsonPath$4.doParseWith(JsonPath.java:967)
    at io.restassured.path.json.JsonPath$JsonParser.parseWith(JsonPath.java:1047)
    at io.restassured.path.json.JsonPath.get(JsonPath.java:202)
    at files.Dynamic.addBook(Dynamic.java:21)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.testng.internal.invokers.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:139)
    at org.testng.internal.invokers.TestInvoker.invokeMethod(TestInvoker.java:664)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethod(TestInvoker.java:227)
    at org.testng.internal.invokers.MethodRunner.runInSequence(MethodRunner.java:50)
    at org.testng.internal.invokers.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:957)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethods(TestInvoker.java:200)
    at org.testng.internal.invokers.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:148)
    at org.testng.internal.invokers.TestMethodWorker.run(TestMethodWorker.java:128)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.testng.TestRunner.privateRun(TestRunner.java:848)
    at org.testng.TestRunner.run(TestRunner.java:621)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:443)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:437)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:397)
    at org.testng.SuiteRunner.run(SuiteRunner.java:336)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:95)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1280)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1200)
    at org.testng.TestNG.runSuites(TestNG.java:1114)
    at org.testng.TestNG.run(TestNG.java:1082)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:115)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)
Caused by: groovy.json.JsonException: Lexing failed on line: 1, column: 1, while reading 'h', no possible valid JSON value or punctuation could be recognized.
    at groovy.json.JsonLexer.nextToken(JsonLexer.java:86)
    at groovy.json.JsonLexer$nextToken.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:130)
    at io.restassured.internal.path.json.ConfigurableJsonSlurper.parse(ConfigurableJsonSlurper.groovy:97)
    at io.restassured.internal.path.json.ConfigurableJsonSlurper$parse.callCurrent(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:171)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:185)
    at io.restassured.internal.path.json.ConfigurableJsonSlurper.parseText(ConfigurableJsonSlurper.groovy:83)
    at io.restassured.path.json.JsonPath$4$1.method(JsonPath.java:965)
    at io.restassured.path.json.JsonPath$ExceptionCatcher.invoke(JsonPath.java:1000)
    ... 32 more

====================

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>2.20.0</version>
    <scope>test</scope>
</dependency>