diff --git a/lib/Epub/Epub.cpp b/lib/Epub/Epub.cpp
index 1477d72..a3edac8 100644
--- a/lib/Epub/Epub.cpp
+++ b/lib/Epub/Epub.cpp
@@ -322,6 +322,11 @@ int Epub::getTocItemsCount() const { return toc.size(); }
 
 // work out the section index for a toc index
 int Epub::getSpineIndexForTocIndex(const int tocIndex) const {
+  if (tocIndex < 0 || tocIndex >= toc.size()) {
+    Serial.printf("[%lu] [EBP] getSpineIndexForTocIndex: tocIndex %d out of range\n", millis(), tocIndex);
+    return 0;
+  }
+
   // the toc entry should have an href that matches the spine item
   // so we can find the spine index by looking for the href
   for (int i = 0; i < spine.size(); i++) {
@@ -336,6 +341,11 @@ int Epub::getSpineIndexForTocIndex(const int tocIndex) const {
 }
 
 int Epub::getTocIndexForSpineIndex(const int spineIndex) const {
+  if (spineIndex < 0 || spineIndex >= spine.size()) {
+    Serial.printf("[%lu] [EBP] getTocIndexForSpineIndex: spineIndex %d out of range\n", millis(), spineIndex);
+    return -1;
+  }
+
   // the toc entry should have an href that matches the spine item
   // so we can find the toc index by looking for the href
   for (int i = 0; i < toc.size(); i++) {
@@ -348,13 +358,21 @@ int Epub::getTocIndexForSpineIndex(const int spineIndex) const {
   return -1;
 }
 
-size_t Epub::getBookSize() const { return getCumulativeSpineItemSize(getSpineItemsCount() - 1); }
+size_t Epub::getBookSize() const {
+  if (spine.empty()) {
+    return 0;
+  }
+  return getCumulativeSpineItemSize(getSpineItemsCount() - 1);
+}
 
 // Calculate progress in book
 uint8_t Epub::calculateProgress(const int currentSpineIndex, const float currentSpineRead) {
+  size_t bookSize = getBookSize();
+  if (bookSize == 0) {
+    return 0;
+  }
   size_t prevChapterSize = (currentSpineIndex >= 1) ? getCumulativeSpineItemSize(currentSpineIndex - 1) : 0;
   size_t curChapterSize = getCumulativeSpineItemSize(currentSpineIndex) - prevChapterSize;
-  size_t bookSize = getBookSize();
   size_t sectionProgSize = currentSpineRead * curChapterSize;
   return round(static_cast<float>(prevChapterSize + sectionProgSize) / bookSize * 100.0);
 }
diff --git a/lib/ZipFile/ZipFile.cpp b/lib/ZipFile/ZipFile.cpp
index 30b44f8..f55bb85 100644
--- a/lib/ZipFile/ZipFile.cpp
+++ b/lib/ZipFile/ZipFile.cpp
@@ -62,6 +62,10 @@ long ZipFile::getDataOffset(const mz_zip_archive_file_stat& fileStat) const {
   const uint64_t fileOffset = fileStat.m_local_header_ofs;
 
   FILE* file = fopen(filePath.c_str(), "r");
+  if (!file) {
+    Serial.printf("[%lu] [ZIP] Failed to open file for reading local header\n", millis());
+    return -1;
+  }
   fseek(file, fileOffset, SEEK_SET);
   const size_t read = fread(pLocalHeader, 1, localHeaderSize, file);
   fclose(file);
@@ -104,6 +108,10 @@ uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const boo
   }
 
   FILE* file = fopen(filePath.c_str(), "rb");
+  if (!file) {
+    Serial.printf("[%lu] [ZIP] Failed to open file for reading\n", millis());
+    return nullptr;
+  }
   fseek(file, fileOffset, SEEK_SET);
 
   const auto deflatedDataSize = static_cast<size_t>(fileStat.m_comp_size);
@@ -175,6 +183,10 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
   }
 
   FILE* file = fopen(filePath.c_str(), "rb");
+  if (!file) {
+    Serial.printf("[%lu] [ZIP] Failed to open file for streaming\n", millis());
+    return false;
+  }
   fseek(file, fileOffset, SEEK_SET);
 
   const auto deflatedDataSize = static_cast<size_t>(fileStat.m_comp_size);
diff --git a/src/activities/reader/EpubReaderActivity.cpp b/src/activities/reader/EpubReaderActivity.cpp
index f4e4536..dd6dd04 100644
--- a/src/activities/reader/EpubReaderActivity.cpp
+++ b/src/activities/reader/EpubReaderActivity.cpp
@@ -33,13 +33,14 @@ void EpubReaderActivity::onEnter() {
 
   epub->setupCacheDir();
 
-  if (SD.exists((epub->getCachePath() + "/progress.bin").c_str())) {
-    File f = SD.open((epub->getCachePath() + "/progress.bin").c_str());
+  File f = SD.open((epub->getCachePath() + "/progress.bin").c_str());
+  if (f) {
     uint8_t data[4];
-    f.read(data, 4);
-    currentSpineIndex = data[0] + (data[1] << 8);
-    nextPageNumber = data[2] + (data[3] << 8);
-    Serial.printf("[%lu] [ERS] Loaded cache: %d, %d\n", millis(), currentSpineIndex, nextPageNumber);
+    if (f.read(data, 4) == 4) {
+      currentSpineIndex = data[0] + (data[1] << 8);
+      nextPageNumber = data[2] + (data[3] << 8);
+      Serial.printf("[%lu] [ERS] Loaded cache: %d, %d\n", millis(), currentSpineIndex, nextPageNumber);
+    }
     f.close();
   }
 
@@ -382,7 +383,7 @@ void EpubReaderActivity::renderStatusBar() const {
     const auto tocItem = epub->getTocItem(tocIndex);
     title = tocItem.title;
     titleWidth = renderer.getTextWidth(SMALL_FONT_ID, title.c_str());
-    while (titleWidth > availableTextWidth) {
+    while (titleWidth > availableTextWidth && title.length() > 11) {
       title = title.substr(0, title.length() - 8) + "...";
       titleWidth = renderer.getTextWidth(SMALL_FONT_ID, title.c_str());
     }
diff --git a/src/main.cpp b/src/main.cpp
index 9f25569..a518201 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -159,7 +159,12 @@ void setup() {
   SPI.begin(EPD_SCLK, SD_SPI_MISO, EPD_MOSI, EPD_CS);
 
   // SD Card Initialization
-  SD.begin(SD_SPI_CS, SPI, SPI_FQ);
+  if (!SD.begin(SD_SPI_CS, SPI, SPI_FQ)) {
+    Serial.printf("[%lu] [   ] SD card initialization failed\n", millis());
+    exitActivity();
+    enterNewActivity(new FullScreenMessageActivity(renderer, inputManager, "SD card error", BOLD));
+    return;
+  }
 
   SETTINGS.loadFromFile();