diff --git a/lib/Epub/Epub.cpp b/lib/Epub/Epub.cpp
index 9c4b058..64727bc 100644
--- a/lib/Epub/Epub.cpp
+++ b/lib/Epub/Epub.cpp
@@ -167,7 +167,10 @@ bool Epub::parseTocNavFile() const {
   }
   const auto navSize = tempNavFile.size();
 
-  TocNavParser navParser(contentBasePath, navSize, bookMetadataCache.get());
+  // Note: We can't use `contentBasePath` here as the nav file may be in a different folder to the content.opf
+  // and the HTMLX nav file will have hrefs relative to itself
+  const std::string navContentBasePath = tocNavItem.substr(0, tocNavItem.find_last_of('/') + 1);
+  TocNavParser navParser(navContentBasePath, navSize, bookMetadataCache.get());
 
   if (!navParser.setup()) {
     Serial.printf("[%lu] [EBP] Could not setup toc nav parser\n", millis());
diff --git a/lib/Epub/Epub/BookMetadataCache.cpp b/lib/Epub/Epub/BookMetadataCache.cpp
index 06b4f45..52e4809 100644
--- a/lib/Epub/Epub/BookMetadataCache.cpp
+++ b/lib/Epub/Epub/BookMetadataCache.cpp
@@ -9,7 +9,7 @@
 #include "FsHelpers.h"
 
 namespace {
-constexpr uint8_t BOOK_CACHE_VERSION = 3;
+constexpr uint8_t BOOK_CACHE_VERSION = 4;
 constexpr char bookBinFile[] = "/book.bin";
 constexpr char tmpSpineBinFile[] = "/spine.bin.tmp";
 constexpr char tmpTocBinFile[] = "/toc.bin.tmp";
diff --git a/lib/Epub/Epub/parsers/ContentOpfParser.cpp b/lib/Epub/Epub/parsers/ContentOpfParser.cpp
index 2c90d01..aee7e57 100644
--- a/lib/Epub/Epub/parsers/ContentOpfParser.cpp
+++ b/lib/Epub/Epub/parsers/ContentOpfParser.cpp
@@ -167,7 +167,7 @@ void XMLCALL ContentOpfParser::startElement(void* userData, const XML_Char* name
       if (strcmp(atts[i], "id") == 0) {
         itemId = atts[i + 1];
       } else if (strcmp(atts[i], "href") == 0) {
-        href = self->baseContentPath + atts[i + 1];
+        href = FsHelpers::normalisePath(self->baseContentPath + atts[i + 1]);
       } else if (strcmp(atts[i], "media-type") == 0) {
         mediaType = atts[i + 1];
       } else if (strcmp(atts[i], "properties") == 0) {
@@ -243,7 +243,7 @@ void XMLCALL ContentOpfParser::startElement(void* userData, const XML_Char* name
           break;
         }
       } else if (strcmp(atts[i], "href") == 0) {
-        textHref = self->baseContentPath + atts[i + 1];
+        textHref = FsHelpers::normalisePath(self->baseContentPath + atts[i + 1]);
       }
     }
     if ((type == "text" || (type == "start" && !self->textReferenceHref.empty())) && (textHref.length() > 0)) {
diff --git a/lib/Epub/Epub/parsers/TocNavParser.cpp b/lib/Epub/Epub/parsers/TocNavParser.cpp
index b8a4e7f..454b243 100644
--- a/lib/Epub/Epub/parsers/TocNavParser.cpp
+++ b/lib/Epub/Epub/parsers/TocNavParser.cpp
@@ -1,5 +1,6 @@
 #include "TocNavParser.h"
 
+#include <FsHelpers.h>
 #include <HardwareSerial.h>
 
 #include "../BookMetadataCache.h"
@@ -140,7 +141,7 @@ void XMLCALL TocNavParser::endElement(void* userData, const XML_Char* name) {
   if (strcmp(name, "a") == 0 && self->state == IN_ANCHOR) {
     // Create TOC entry when closing anchor tag (we have all data now)
     if (!self->currentLabel.empty() && !self->currentHref.empty()) {
-      std::string href = self->baseContentPath + self->currentHref;
+      std::string href = FsHelpers::normalisePath(self->baseContentPath + self->currentHref);
       std::string anchor;
 
       const size_t pos = href.find('#');
diff --git a/lib/Epub/Epub/parsers/TocNcxParser.cpp b/lib/Epub/Epub/parsers/TocNcxParser.cpp
index b1fbb2f..3e59451 100644
--- a/lib/Epub/Epub/parsers/TocNcxParser.cpp
+++ b/lib/Epub/Epub/parsers/TocNcxParser.cpp
@@ -1,5 +1,6 @@
 #include "TocNcxParser.h"
 
+#include <FsHelpers.h>
 #include <HardwareSerial.h>
 
 #include "../BookMetadataCache.h"
@@ -159,7 +160,7 @@ void XMLCALL TocNcxParser::endElement(void* userData, const XML_Char* name) {
     // This is the safest place to push the data, assuming <navLabel> always comes before <content>.
     // NCX spec says navLabel comes before content.
     if (!self->currentLabel.empty() && !self->currentSrc.empty()) {
-      std::string href = self->baseContentPath + self->currentSrc;
+      std::string href = FsHelpers::normalisePath(self->baseContentPath + self->currentSrc);
       std::string anchor;
 
       const size_t pos = href.find('#');